Upcoming changes to the RC2014 bus and ecosystem

[Spencer Owen]

Almost 4 years ago, when I listed the first RC2014 PCBs on Tindie, I tried to come up with a description of what an RC2014 is, and ended up with this;

RC2014 is a simple 8 bit Z80 based modular computer. It is inspired by the home built computers of the late 70s and computer revolution of the early 80s. It is not a clone of anything specific, but there are suggestions of the ZX81, UK101, S100, Superboard II and Apple I in here. It nominally has 8K ROM, 32K RAM, runs at 7.3728MHz and communicates over serial at 115,200 baud.

Since then, there has been a few questions raised about things like which backplane pins should be used for 3v3, what is the best way to address 16 bit I/O ports, what bus termination is used for really fast CPU, how is SPI or I2C supported on the backplane, how should IEI/IEO be addressed on the bus, what is the finest pitch surface mount parts that can be used, how should the physical bus be changed... etc.  So, with that in mind, the description on all RC2014 products going forward will be;

RC2014 is a simple 8 bit Z80 based modular computer. It is inspired by the home built computers of the late 70s and computer revolution of the early 80s. It is not a clone of anything specific, but there are suggestions of the ZX81, UK101, S100, Superboard II and Apple I in here. It nominally has 8K ROM, 32K RAM, runs at 7.3728MHz and communicates over serial at 115,200 baud.

The RC2014 was never designed to run super fast CPUs with a huge range of exotic peripherals and loads of memory.  It was designed to be simple.  Simple to build, simple to understand, and simple to program.

So, for the various questions people have been asking, it does not have a 3v3 pin on the backplane. It does not have 16 bit I/O ports.  It does not have any bus termination.  SPI or I2C are not supported on the backplane.  The RC2014 bus does not support IEI/IEO modules.  Through-hole components are used. And the physical bus will not be changing.

I appreciate that this might not be the response that a few of you were looking for.  Everybody that has bought an RC2014 kit would have read the description above.  If you read that and expected a Z280 running at 33MHz with 4Mb RAM, SD storage with 16 bit IO peripherals and I2C, then, I'm sorry, but that is not what the RC2014 is.  And not what it is going to be.  Having a pissing competition to see who has the fasted CPU, or the most memory, or the most complex OS is not what the RC2014 is about.  If it comes to an arms race then just jump straight to the finish line and get a Raspberry Pi or some modern thing.  That'll have all the memory, ports, speed and expansion you could possibly want.

There are currently well over 12,000 RC2014 PCBs out there in the wild which work just fine and by definition, totally comply with the RC2014 specification and ethos.  [No RC2014 modules are "Problem Modules" particularly when there's almost a thousand of them out there doing exactly what they were designed to do]  I don't have any figures on how many 3rd party boards "designed for RC2014" have been sold, but I know that a lot have been designed.  Most of these worth within the RC2014 constraints, and there are some really great peripherals or replacement modules.  Some use some of the spare pins for their own use.  It is totally ok to use spare pins for whatever you want.  It's totally ok to use extra pins for whatever you want.  It's even totally ok to reuse existing pins for something totally different.  However, it should be clear that anything which will not plug in to and run on a RC2014 is not compatible with the RC2014.  

I know that a few people on this group are really pushing, and well exceeding the boundaries of what the RC2014 was designed for.  This is great, and I admire the work you guys are putting in to this.  But it must be pointed out that the vast majority of people got their RC2014 because of the simplicity.  Because it was something that they could build themselves.  Because it was reminiscent of what they build as youngsters or saw their parents working with.

Sorry that this email has been quite a bit longer than I expected, and probably a bit rambley in places.

tl;dr RC2014 will not be changing

Thanks

Spencer - putting on his fireproof suit

[karlab]

Hi Spencer

I appreciate you want to keep the RC2014 system as it is.

The rc2014 is probably one of the best educational platforms for computer design and the brilliant part is the backplane and modular design.

It is important to have in mind that while your system is a good starting platform, users may want to experiment, try new things, new functions, new circuits, new CPUs.

Basically, the users are moving on, and some may be moving away from RC2014. It is not a speed race, but it may be pushing the boundaries.

Users have these projects because it's fun, they want a challenge and it's educationally, and that's not a bad thing.

And the whole RC2014 community is benefiting from this development.

Making extended standards do not threaten the RC2014 platform, but facilitate interoperability between advanced projects.

cheers

Karl

wearing fireproof gloves ;)

[Eric Matecki]

Hi Spencer,

This is great, as it is an 'official' answer many where waiting for (and for some time for some of the topics).

In all this, *I* am only interested in IEI/IEO, now I know the best way is simply to use flying wires between modules.

Because whatever pins are used on the backplane for IEI/IEO, there will be a conflict in the future with another board.

Eric M.

[Alan Cox]

> I appreciate that this might not be the response that a few of you were looking for. Everybody that has bought an RC2014 kit would have read the description above. If you read that and expected a Z280 running at 33MHz with 4Mb RAM, SD storage with 16 bit IO peripherals and I2C, then, I'm sorry, but that is not what the RC2014 is. And not what it is going to be. Having a pissing competition to see who has the fasted CPU, or the most memory, or the most complex OS is not what the RC2014 is about. If it comes to an arms race then just jump straight to the finish line and get a Raspberry Pi or some modern thing. That'll have all the memory, ports, speed and expansion you could possibly want.

36MHz works fine - I have wait states on the CPU but that's because
the RAM isn't quite fast enough 8)

> No RC2014 modules are "Problem Modules"

It would be nice to get the CF module more reliable. IMHO that one
does qualify as a problem module if you are unlucky on your choice of
CF card.

We probably do need a proper 'extended standard' beyond RC2014 just so
the addons interwork, even if it's not a Spencer standard - and we
seem to kind of have that already.

Alan

[Derry UK]

There is more than one way to skin a cat. That is why I have a dozen or so z80 systems. Th Rc2014 wasn't one of my favourites but I liked the idea of plug in boards and so do a lot of people it seems.

I am now at my happiest with a Teensy running emulated CPM. The DOS formatted SD card makes life a breeze but more importantly it allows me to write Z80 assembler all day long.

Derry.

PS I will get that text editor finished one day ....

PPS I don't read a Teensy forum for my Z80 fix I read this one.

[Steve Cousins]

Spencer

Thanks for clarifying the official position on the future of RC2014. 

A while back you provided, on this forum, some provisional guidance on the use of additional bus pins:

I've been musing over enhancements to the backplane for a little while now, and whilst nothing is set in stone, the pin layout would follow this;

   Enhanced Standard

A31 1 1 A15

A30 2 2 A14

A29 3 3 A13

A28 4 4 A12

A27 5 5 A11

A26 6 6 A10

A25 7 7 A9

A24 8 8 A8

A23 9 9 A7

A22 10 10 A6

A21 11 11 A5

A20 12 12 A4

A19 13 13 A3

A18 14 14 A2

A17 15 15 A1

A16 16 16 A0

Gnd 17 17 Gnd

5v 18 18 5v

RFSH 19 19 M1

Page 20 20 Reset

Clock2 21 21 Clock

BUSACK 22 22 INT

HALT 23 23 MREQ

BUSRQ 24 24 WR

WAIT 25 25 RD

NMI 26 26 IO

I think some of us have been basing our "designed for RC2014" on this guidance. Are you saying this guidance is not correct?

You say "However, it should be clear that anything which will not plug in to and run on a RC2014 is not compatible with the RC2014.". Does that mean anything that does not work on a backplane Pro can no longer be described as RC2014 compatible?

Steve

[Phillip Stevens]

+1.

[Greg Holdren]

Pffftt, Right, people take your MB memory hogging speed demon OS pissing contest elsewhere. It is not needed to support the official RC2014 ca$h cow.

Greg

[Richard Lewis]

(disclaimer: this will start off slow but I'll get to the point soon enough...) 

I'm only speaking for myself but basically I'm bored. To elaborate, when I first started building my kit a "pull up" to me was something my daughter wore after graduating from nappies. I got my system up and running, booted CP/M, played ZORK, Star Trek and fired up Wordstar for the first time in 30 years, Next I relearned Z80 assembler which I hadn't touched since I was a kid. Then I build pretty much every board available in the RC2014 ecosystem. I studied the schematics to learn about how address decoding works, then Iearned that a pull-up is not something you go to the bathroom in. Fast forward to today and I'm using Kicad to build my own boards. But then what to build? In my mind it's pretty much all been built. The last board I created of my own design was a THT "Bus Monitor" which was so similar to Dr Bakers (probably because we both lifted the idea from Steve Ciarcia) that I was originally going to call it "The Dead Horse" module. However, I learned quite a bit from that exercise. The 2nd board I designed was a Z80, SIO4, PIO, CTC, SRAM, EEPROM, CPLD for glue, all in SMT QFP packages and it fit on one standard 4-layer rc2014 card with room to spare. Never sent off for the boards because it didn't do anything special just was fun to create. An hour ago I finished soldering a QFP-144 with 0.65mm pitch without any issues. A year ago if you threw a QFP in front of me and said: "Solder this!" I would reply: "Are you high? No way..." Before the rc2014 I had built kits (clocks, a stereo, various small things) but had treated them a "paint by number" exercise. The rc2014 was the first kit to actually entice me to learn more. 

OK, sorry for the rambling. Just wanted to provide some context. Even though I'm old enough to have been involved in the "retro era" and have a bit nostalgia from the days when I was first learning how to write a game on a TRS-80, I'm pretty much stuck in the present. The original rc2014 kit that I put together has subsequently been cannibalized for parts and is in a box somewhere. I just recently moved over to the Z180. I like discovering new chips and going blind attempting to solder ridiculously small parts. So I've learned things and have been progressively moving up levels. 

Now I'll get to the point. I see the future of the RC2014 ecosystem as "leveling up" with the user. Received a grab bag of Diligent PMods in the mail the other day: air pressure, ADC, temperature, servo control etc etc etc and all work with SPI or I2C. My thought was: "Wouldn't this be cool to build into the RC2014 world and for example access a motor control module which uses 201X parts from MSBasic written in 1980?"

[Richard Lewis]

Hi Greg, I am very bad at detecting sarcasm which I assume this is. My interpretation is that maybe we should split off into separate forums or groups? A group for vanilla RC2014: ask questions about the kit, get help if something is not working, announce new products and releases. A group for discussion around RC2014 compatible boards and perhaps a group to talk about anything related to the Z80. I don't think Google Groups allows subgrouping or dividing groups into forums? 

[Richard Lewis]

Now I'll get to the point. I see the future of the RC2014 ecosystem as "leveling up" with the user. Received a grab bag of Diligent PMods in the mail the other day: air pressure, ADC, temperature, servo control etc etc etc and all work with SPI or I2C. My thought was: "Wouldn't this be cool to build into the RC2014 world and for example access a motor control module which uses 201X parts from MSBasic written in 1980?"

Wanted to expand on this last point. It is ridiculously easy (bordering on trivial) to plug a SPI peripheral into a RaspPI, Arduino or (not as trivial, but still reasonable easy) an FPGA board. Just download the sample code, plugin the wires and "go". I'm already yawning as I type this... What would be more fun is getting it work with retro hardware. 

[John Kennedy]

Maybe there is a need for some kind of expansion system, that still at the end of the day, can be communicate with the RC system (so you can write Z80 code to interface it) but which opens up in a more powerful buss for lots of different processors, sensors, internet connections etc etc? If that became a standard, there could be an entirely new and modern system for you to play with BUT it would still link to the good old RC..

[Phillip Stevens]

Richard Lewis wrote:

Now I'll get to the point. I see the future of the RC2014 ecosystem as "leveling up" with the user. Received a grab bag of Diligent PMods in the mail the other day: air pressure, ADC, temperature, servo control etc etc etc and all work with SPI or I2C.

Sometimes, when "leveling up" it is time to move on to new things (without necessarily discarding the old).

This conversation is particularly relevant, IMHO, for things like the Arduino platform too.

In the midst of a raft of new 32-bit MCU (sponsored by companies wanting to get to the maker market), the Arduino UNO soldiers on.

Why is that? Well, I guess because the Uno is simple to use for people starting out, and remains relevant for others too. So the Arduino developer community is becoming fragmented because of the multitude of platforms they're trying to support, but they're forgetting that it is the beginner that is their customer.

For example, I have two RC2014 systems. One of which is an original small low card #256, which lives in my e-memorabilia drawer.

The other updated CP/M RC2014, which lives on my desk alongside my z180 platform.

I use them both daily, and love the fact that I can test my code in either z80 or z180 environments with a very simple and robust workflow, just by plugging a USB.

When I started building my z180, I didn't try to fit it into RC2014 format, because I had my own particular goals for "leveling up". Point I'm making is that not everything has to be made to be RC2014 compatible. Strike out on your own, be like the Steve Ciarcia's of the world. ;-)

Rejoice in what is the spirit of the RC2014. "RC2014 is a simple 8 bit Z80 based modular computer. It is inspired by the home built computers of the late 70s and computer revolution of the early 80s." If you, personally, want to do something else challenging then that's great too. Leveling up our knowledge is what this is all about.

Cheers, Phillip

[Greg Holdren]

Richard,

Yes, very much meant as sarcasm. ;)

Not really digging the tone of the message. Really odd. Spencer could just say the "Official" bus spec will not change or whatever and it is not expanding beyond what it is now. It is almost like that this has been brewing for awhile and it just blew up. Maybe the advanced discussions here are scaring off the beginning/potential Z80-RC2014 users.

Yeah, I was thinking that another group "80-pin bus", or whatever group name, could be created for advanced discussions and the current for supporting kit builders and official use. This happens to political/specification bodies all the time, split and bail. Only Spencer can tell use if that is the case.

Greg

[Richard Lewis]

Hi Phillip, I get it. Yesterday I used a dusty UNO to program a si5153 clock generator board over SPI because the creator of the board emailed me an Arduino sketch. However jumping back into the Arduino IDE was the electronic equivalent of being castrated. I have moved on. I guess I could sit down,  build out a brand new system and bus around the eZ80 for example, dump it on Tindie and wait for the money to not roll in. I could discuss this new system here and no one would listen and possibly get reprimanded for being off topic. Or I could be part of an established community, try something new, bounce it off of people and see if anyone "buys" into it. 

I don't necessarily include myself in this category but if the "experts" get scared off I have no reason to stick around. Not really interested in helping someone write a very basic algorithm in z80 asm to convert BCD to binary or to help someone with poor soldering skills. I used to but now starting to find it tedious. Would rather talk about if it's possible to bitbang SPI or I2C with a Z80. 

[Richard Lewis]

80-pin bus would be a good name for a punk rock band.,,,

[Phillip Stevens]

Richard Lewis wrote:

I don't necessarily include myself in this category but if the "experts" get scared off I have no reason to stick around. Not really interested in helping someone write a very basic algorithm in z80 asm to convert BCD to binary or to help someone with poor soldering skills. I used to but now starting to find it tedious. Would rather talk about if it's possible to bitbang SPI or I2C with a Z80.

The RC2014 community needs to keep the discussion "simple 8 bit Z80 based modular computer" related, but there's strong interest in other topics which keep the place animated.

In the absence of a better solution, perhaps just adding an [off topic] subject tag to general what-if z80 / z180 thought bubble threads would be enough to achieve both outcomes?

But, I don't think that even the BDFL can edit posts or their subject lines to suit. It is a limitation of Google Groups, that there's no hierarchy of topics or post editing, unfortunately.

Cheers, Phillip

[Richard Deane]

I find the rc2014 group very invigorating, helpful and generally friendly, covering a range of topics from simple to advanced. I would hate that to change. I find it full of info and ideas, a much better vehicle than the unofficial Facebook group which in my view hasn't picked up traction yet. If we all drift off to other groups we will have lost something good.
I think Spencer has maintained a fair level of tolerance for the messages that drift off strict rc2014 and I believe they can strengthen the group, but rightly may require moderation.
Keep up the good work, everyone!
Richard

[Mike Strange]

Spencer, your definition and clarity in your intentions are exactly what has been needed. There are some extremely clever people here that are able to develop hardware and software that must surely be way beyond even the comprehension of most people who have purchased your RC2014 systems. Indeed, I wonder just how many people have actually taken their initial kit any further than your designs and have no plans to do anything else. 

There is the danger that folk joining the Group before they make a purchase may be put off by the wonderful high-level discussions that now dominate the posts here and decide against a purchase. It would be interesting to get some input from people who are beginners and just want to have a dabble at the basic level.

Perhaps the solution might be to migrate to a proper forum so that the high level activities can be on boards of their own within the forum leaving the conventional RC2014 requests for help and the solutions much more visible and accessible. As it is even the really clever stuff is soon buried in this serial nature of Google Groups that doesn't even have the means of establishing a repository for files and photographs or even sticky posts with links to help and developments.  Yahoo Groups are great for storage but posts are still serial (and their demise is threatened); is there anything that provides both features (message grouping and information storage)?

All the best

Mike

On Sunday, 16 June 2019 20:39:20 UTC+1, Spencer Owen wrote:

[Alan Cox]

Some thoughts

- Please don't call any extended bus 80pin bus or 80-bus or stuff like
that because there already is an 80bus. It's what all the old Nascom
and related machines used so it's already a thing.
- SPI is 1985 so at least as legacy as IDE (1986), and way more so
than compact flash (1994) 8)
- I still think SPI and I²C are important to attract people as it
means you could build machines that do interesting stuff more easily -
even if they are bitbang. You simply can't get most of the old old non
SPI or I²C sensors any more, they no longer exist
- SPI is going to matter in time, because compact flash is going away

One approach that strikes me is to define (or more likely borrow) a
completely unrelated SPI/I²C type bus arrangement and then have a
bridge board of some kind that plugs into both busses providing RC2014
on one bus and I²C etc on the other whether it is legacy in design or
modern wouldn't matter (or indeed whether it was a board or a bunch of
wires from a Z80PIO RC2014 card).

Alan

[Greg Holdren]

Alan,

No, that was an just an example or place holder for some name.

I'm sure a suitable existing bus standard exist that will work if not

the enhanced 80 pin bus.

I2C is good for sensors or infrequent data but data "en mas" it isn't.

Greg

[Jay Cotton]

I like the ideas of a bus to bus board that implements i2c and spi in one and

provide a bus on the other side.  We already have both i2c and spi designs, seems

to me a merge is called for.

On Monday, June 17, 2019 at 6:30:00 AM UTC-7, Alan Cox wrote:

[Michael Stevens]

I do feel a little disappointed with the attitude from Spencer.  If not for the people that have jumped on your platform would have had far fewer sales. When you want to use terms like pissing competition tells me you are losing the plot. Your technical ability is much more limited than the ecosystem that sprang up behind this, My boards will be tagged with "Maybe not RC2014 Compatible" Will just give them away so you should not feel any stress on what you claim as your Copyright. Do or can you prove have actually taken out a copyright on the name RC2014? 

[Steve Cousins]

Hi Michael

Spencer's website states that RC2014 is a registered trademark. See text below.

Steve

If you wish to design your own modules, you are, of course, free to use whatever shape, size or pin arrangement you wish.  However, keeping to the above guidelines should give your modules compatibility with other RC2014 modules.  If your module may be of use to other RC2014 owners, please consider sharing your design or selling them yourself.  I’m happy to help you with this and to spread the word.  Note that “RC2014” is a registered trademark, so you are not allowed to call your module “RC2014 [thingy] Module” or use the RC2014 logo.  However, feel free to mark your modules as “Designed for RC2014”

[Alan Cox]

> Do or can you prove have actually taken out a copyright on the name RC2014?

I think you are more than a bit confused. To start with you don't
copyright names, you file trademarks to protect them.

See registration UK00003213928

Alan

[Michael Stevens]

Thank-you for the much needed correction. 

Virus-free. www.avast.com

--
You received this message because you are subscribed to the Google Groups "RC2014-Z80" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rc2014-z80+...@googlegroups.com.
To post to this group, send an email to rc201...@googlegroups.com.
To view this discussion on the web, visit https://groups.google.com/d/msgid/rc2014-z80/CAK9X0%2BtcD6aPBLtC3DgN3rrAR8P8RfqUi_8J%3DfB4kMnBOUkLNg%40mail.gmail.com.
For more options, visit https://groups.google.com/d/optout.

[Brian Welland]

Steve is quite correct but the use of the term "Designed for RC2014" is often taken a little bit too far. It would be better IMHO if it was worded something like "For possible use in a RC2014 System" as many of the 3rd party modules are not fully compatible with the Backplane Pro. Typical examples are some of those excellent designs which use the 2x40 connector which naturally will not fit as the required additional enhanced header pins are simply not present.

I have used the majority of the available "official RC2014" modules for quite a while, all of which will fit the Pro and to me are thus "RC2014 compatible" - all the rest are simply just modules which can or could be used in a RC2014 type of system but are by no means strictly "RC2014 compatible" and should thus not be considered as such.

Whilst I am not against innovation with the use of different types of CPU's etc in RC2014 type systems to me these are not "RC2014 products" and would be better detailed and implemented under a different forum to this one.

[Greg Holdren]

Cut the pins or no load them or use a shim... Now it is compatible. :)

Greg

[Richard Lewis]

OK, what about a "certified for RC2014" trademark and logo instead? In order to get this the board has to be proven to work on the original or PRO bus and have documentation in a specific format. Like the moniker "Wishbone Compatible" (for those familiar with the OpenCores concept)

On Monday, June 17, 2019 at 11:52:33 AM UTC-7, Brian Welland wrote:

[Marten Feldtmann]

What is this discussion all about ? For me personally nothing changes, I develop my modules based on the RC2014 and change them according to my needs ... perhaps considering stuff from karlab or Steve or others ... perhaps leading me to something totally different.

[Greg Holdren]

Marten,

Spencer is pissed because Bill showed everyone how to turn a $88 RC2014 Mini into a bootable $199 CP/M system without the $88 Full Monty kit. tehehehehehehe :)

...or not.

Greg

[Steve Cousins]

Spencer

You did not answer my questions. eg. the one about your previously published guidance for A16 to A31.

Steve

On Sunday, 16 June 2019 22:55:06 UTC+1, Steve Cousins wrote:

Spencer

Thanks for clarifying the official position on the future of RC2014. 

A while back you provided, on this forum, some provisional guidance on the use of additional bus pins:

I've been musing over enhancements to the backplane for a little while now, and whilst nothing is set in stone, the pin layout would follow this;

   Enhanced Standard

A31 1 1 A15

A30 2 2 A14

A29 3 3 A13

A28 4 4 A12

A27 5 5 A11

A26 6 6 A10

A25 7 7 A9

A24 8 8 A8

A23 9 9 A7

A22 10 10 A6

A21 11 11 A5

A20 12 12 A4

A19 13 13 A3

A18 14 14 A2

A17 15 15 A1

A16 16 16 A0

Gnd 17 17 Gnd

5v 18 18 5v

RFSH 19 19 M1

Page 20 20 Reset

Clock2 21 21 Clock

BUSACK 22 22 INT

HALT 23 23 MREQ

BUSRQ 24 24 WR

WAIT 25 25 RD

NMI 26 26 IO

I think some of us have been basing our "designed for RC2014" on this guidance. Are you saying this guidance is not correct?

You say "However, it should be clear that anything which will not plug in to and run on a RC2014 is not compatible with the RC2014.". Does that mean anything that does not work on a backplane Pro can no longer be described as RC2014 compatible?

Steve

[Alan Cox]

Brian Welland <brwella...@gmail.com> wrote:

> Steve is quite correct but the use of the term "Designed for RC2014" is often taken a little bit too far. It would be better IMHO if it was worded something like "For possible use in a RC2014 System" as many of the 3rd party modules are not fully compatible with the Backplane Pro. Typical examples are some of those excellent designs which use the 2x40 connector which naturally will not fit as the required additional enhanced header pins are simply not present.

I think we probably do need a unified definition for a strict superset
of RC2014, but that should probably also say that a board that does
not need to use the extra pins should be kept to RC2014, so there
isn't an unneeded split. The 80 pin bus already exists courtesy of
Steve and seems to have been laid down as a sort of standard. We could
even call it "PC80" if it needs a name (the Pissing-Contest 80pin bus)
8)

> Whilst I am not against innovation with the use of different types of CPU's etc in RC2014 type systems to me these are not "RC2014 products" and would be better detailed and implemented under a different forum to this one.

Then you lose the very people you want on this list for helping people
debug boards and spotting design errors.

Alan

[karlab]

The enclosed picture is how I visualize the various BUS standards.

We can then start discussing the layout of the RC80 and RC40 bus, and leave the RC2014 bus alone.

Karl

[Mark T]

Hi Karl, I think i would consider RST2 as the PAGE signal as I have never seen it used as a reset.

I think the X0 to X7 as user defined pins is reasonable, its unlikely to need 32 bit address bus.

A16 to A23 raises a few questions. I think z180 would only use A16 to A19, and Z280 would support A16 to A23. Should extended memory modules be configured to decode the full address A16 to A23 to support later use with 24 bit addressing?

If extended address decoding is included for memory, the address lines should not be floating, does this mean the processor boards should include drive for the full 24 bit address? Or should some provision be included in the memory module?

Experimenting with 16 bit data bus may need separate upper and lower byte control, but would fit into the X0 to X7 user defined pins.

Mark

[karlab]

I agree Mark

With the extra bus pins it is possible to run processors like 8088, 68008 and Z180/Z280 and at the same time keep compatibility with existing modules.

Karl

[Marten Feldtmann]

Perhaps one should restrict ourselves to some kind of Z80 bus system, so that means:

* 08 bit databus (mean Z80, Z180, ez80 and Z280) - this means, NO D8 .. D15 - this still gives a large playground field

* 20 bit addressbus (means Z80, additional space for Z180 and ez80 and Z280)

And my personal likes:

* additional INT-lines

* IEO/IEI problem

* 3.3V

* SPI could be used with CLK2,RX2 and TX2

* i2c for a base bus needs only some lines

So, this bus is not considered to be used with 68K chips (16 bit) etc. Even though I've bought now numerous 68k chips to get into this direction, I perhaps would rather start with a new bus for this kind of CPU.

[Richard Lewis]

Now I have to "Old MacDonald song stuck in my head"

On Tuesday, June 18, 2019 at 7:57:30 AM UTC-7, Marten Feldtmann wrote:

Perhaps one should restrict ourselves to some kind of Z80 bus system, so that means:

* IEO/IEI problem

On a more serious note, 3V3, SPI and i2c would be a nice addition. Problem with SPI is that at least 1 master is needed to be defined somewhere. Maybe in relation to the SIO? Or a dedicated high speed serial card that has a SPI master and requisite I2C termination pullups, either managed through a modern MCU or perhaps a 8051 in combo with the Z80 DMA IC?

-Richard 

[Spencer Owen]

Apologies for the radio silence while I've been reading and digesting your comments.  Hopefully I can answer most of your questions.

I think Richards comment "Not really interested in helping someone write a very basic algorithm in z80 asm to convert BCD to binary or to help someone with poor soldering skills. I used to but now starting to find it tedious. Would rather talk about if it's possible to bitbang SPI or I2C with a Z80." sums up why this cropped up.  Helping people get started with the RC2014 is EXACTLY what this group was set up for.  For a lot of people, this is their first big soldering project, or the first time they've dabbled in assembly code, and those are the people which need the help and encouragement the most.  Of course people level up, they learn more, want more of a challenge and exceed what the humble RC2014 provides.  But that does not mean that everybody has levelled up the same, or that new community members instantly have the advanced skills that have taken long standing members years to achieve.  I know that my skills and knowledge have really progressed since building the first RC2014 prototype in 2013, but if I only made kits which were on the bleeding edge of my skill set and dropped everything that no longer challenged me, I would very soon have an audience of one.

It has both amused and saddened me that my "The RC2014 Bus is not going to change" message has gone off in to a discussion on what the new bus will look like, what it's going to be called, how it works with SPI and I2C etc.  For what some of you are trying to do at the moment, it's really pushing the limits of what this kind of interface is designed for, both in terms of pincount and signal integrity.  Maybe something like the PMODS on FPGA boards, or PCI style edge connectors, or SODIMM connectors, or VME bus will be better.  That is all academic really, though, and not relevant to a "The RC2014 Bus is not going to change" thread.  

I'm not really interested in a "Certified for RC2014" scheme, but still perfectly happy for people carry on self-certifying their "Designed for RC2014" as that'll just be quicker and easier for everybody involved.  As the topic of the RC2014 Trademark cropped up, yes, I do hold the trademark for "RC2014".  I got that to offer myself some protection in case knock-off RC2014 kits started coming out of China (I know it'll have very little effect on the Chinese manufacturer, but it should be honoured by Google, eBay etc which will limit their impact), not as a weapon to use against this community.  I do, however, have an obligation to use it when appropriate, and people have been really understanding on the couple of occasions when innocent mistakes have been made.  But I'm certainly not going to be calling the lawyers in if somebody has a "Designed for RC2014" (or even "Maybe not RC2014 Compatible"!) module that maybe uses an extra pin or two.

Which leads me on to Steves question on the use of A16 to A31.  This post Steve is referring to is this one here.  I don't know if my "Nothing is set in stone" comment on that will get me off the hook or not :-)  I guess that a pair of boards which use those extra A16 - A31 lines would work just fine on a RC2014 Backplane Pro (or even Backplane 5 or Backplane 8) if they are supplied with straight pins and jumper cables, similar to how the 64k RAM and Pageable ROM work together on the Backplane 8 with a jumper cable.

Hopefully that's helped clear up some things, and thank you to those which have shown support, either on this thread or via email.

Spencer

[Michael Stevens]

Oops I thought this whole design was taken from Grants site maybe with a few small tweaks. A bus system as in plug-in was conceived and now this whole process Trade-Marked. China would never have an interest as much as so cheap for them is no real customer base. So Spencer has done well already. A community of enthusiasts that support 8 bit and want to expand seems like a good idea. Will put my hands up and say purchased the boards from JLCPCB for the SC114 designed by a renowned member that does hardware and also amazing Z80 firmware. I hope this community continues in the spirit intended. I see or understand Google Groups is free so a zero cost to the RC2014 Brand Name (Trade Mark or whatever it actually is)  

Regards

Mike.

Virus-free. www.avast.com

--
You received this message because you are subscribed to the Google Groups "RC2014-Z80" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rc2014-z80+...@googlegroups.com.

To post to this group, send email to rc201...@googlegroups.com.
To view this discussion on the web, visit https://groups.google.com/d/msgid/rc2014-z80/CAO93PteD%3D0OSA2acYCWYjvtrNPVH1_LTvM7urSSdkjrOhf3QPw%40mail.gmail.com.

For more options, visit https://groups.google.com/d/optout.

Virus-free. www.avast.com

[Steve Cousins]

Hi Spencer,

I think it is good that you have clarified the situation with regard to "changes to the RC2014". Since your published guidance last year I have been waiting for a final official specification for those extra pins.

I am now trying to establish, once and for all, what this means. This is vital, particularly to the future direction of those wanting to push the limits.

So in the context of your clear statements:

"So, with that in mind, the description on all RC2014 products going forward will be; RC2014 is a simple 8 bit Z80 based modular computer. It is inspired by ..."

and

"RC2014 will not be changing"

From that, we know that an RC2014 (and to be clear I mean a genuine Spencer Owen, trademarked, RC2014) is:

* A Z80 based system, not a 6502, Z180, 68000, etc. etc.

* It is 8-bit, not a 16-bit or 4-bit, etc. etc.

* It will not be changing, so will always be the above.

You have made it clear that anyone can make products for the RC2014 ecosystem and label them "Designed for RC2014". You have also indicated some flexibility in the use of "Designed for RC2014" and have apparently been happy with descriptions like "compatible with RC2014" and "<description> for RC2014".

Now to the questions.

Can a 6502 CPU module be described as "Designed for RC2014" and/or "compatible with RC2014"?

Well, it is a different CPU family so it is not software compatible, but it could be designed to be compatible with the RC2014 bus hardware and at least some of the RC2014 modules. So would I be right in thinking "Designed for RC2014" could be used, but "compatible with" needs to carry a few caveats?

The same question asked for other processors would presumably get the same answer if they could also be shown to work with an appropriate range of RC2014 products.

This brings me to modules and backplanes exploiting the extra pins (those available only on an 80-pin connector) and perhaps those using the spare/user pins (which I believe means those available to the user for any purpose they see fit).

If, say, a Z180 CPU module uses the "not cast in stone" allocated A16 to A20 pins, then can it be described as "Designed for RC2014" and/or "compatible with RC2014"?

As you pointed out a ribbon cable between the CPU and memory modules would be a workaround. Also one could plug a Z180 CPU module and Z180 memory module into an 80-pin modular backplane (the extension version with a male connector) and then plug that into any RC2014 backplane to link it to other RC2014 modules.

What about a 16-bit 68000 CPU module? The specification on the rc2014.co.uk website is actually for a 16-bit data bus (it carries D0 to D15 on specified pins). So can a 16-bit processor module be described as "Designed for RC2014" and/or "compatible with RC2014"?

If a pair of modules communicate via I2C or SPI, with those signals on the extra bus pins (available only on an 80-pin connector) or the spare/user pins, can this be described as "Designed for RC2014" and/or "compatible with RC2014"?

If using the extra pins (available only on an 80-pin connector) they could co-exist on an RC2014 system, but not serve any useful purpose (as the I2C or SPI signal pins would not be present). Could this qualify as "compatible" or "designed for"?

If using the spare/user pins (which are part of the RC2014 spec) they could co-exist on an RC2014 system and work on it. Could this qualify as "compatible" or "designed for"?

If the modules also have headers for flying leads between the modules, I assume they could be described as "compatible" or "designed for"?

I am still looking for an answer to:

You say "However, it should be clear that anything which will not plug in to and run on an RC2014 is not compatible with the RC2014.". Does that mean anything that does not work on a backplane Pro can no longer be described as RC2014 compatible?

Steve

[Derry UK]

As I said earlier, there ain't no right or wrong in the world, it just depends on how you look at it.

That is why we are all here, it fills a need.

So can we have more good ideas please and more help for the less enabled of us who just want to get it working.

Derry.

PS I received my "get your old 2014 kit repaired" today so maybe I'll get mine working.

PPS be positive, good ideas and help are positive, slagging off is not good for anyone.

PPPS I have left several online places because of the slagging off, I don't want to leave here but I will if it gets bad.

[Richard Lewis]

Thanks Derry, assurance that the slagging off is temporary, is in response to a one-off-event and is not indicative of the general tone here. I think the community has reached a point where there probably needs to be some kind some kind of enforced stratification. I would like to be able to bring up new ideas, discuss them rationally and not be criticized for it because it is not in the best interest of the beginner. 

Richard

PS  there should be a need for a "repair kit" but it's good none the less that you can get back into the game

[Bill Shen]

Since I'm the guy that's pushing the "Design for RC2014" envelop, I like to go through a few of my boards and see how they fit the description of "design for RC2014".  Since RC2014 Mini is a single board computer that carries the RC2014 logo, I assume RC2014 does not need to be modular in design, that it can be a single-board computer. 

Z80SBC64 is a SBC based on Z80, so it should be "designed for RC2014".
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:z80sbc64

Zuno is Z80SBC64 repackaged for Arduino Mega case.  Its has a RC2014-ish bus and can accept a 40-pin RC2014 connector, but it can only talked to other RC2014 I/O modules.  I believe it is "designed for RC2014"
https://groups.google.com/forum/#!topic/rc2014-z80/GsJMj94DdZA

I believe ZZ80RC is designed for RC2014 because it is a Z280 SBC running in Z80 compatible mode.
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:zz80cf

I also put Z280RC in "designed for RC2014" catagory even though it is Z280 running in 16-bit Z-Bus locally, the signal & timing coming out of the connector is RC2014 I/O timing.
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:z280rc

I would put T68KRC in "designed for RC2014" catagory even though it is 16-bit 68000 in native 68000 timing locally, the CPLD translates the 68000 timing to Z80 timing for signals coming out of the RC2014 connector.
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:t68krc

G8PP is a curious beast because the signals on the connector are programmable.  But even when programmed for Z80, such as G8PP+Z80, it is not "designed for RC2014" this is because 3 of the spare pins are assigned specific Z80 signals. 
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:g8pp:g8ppbasez80
When it is programmed to other microprocessor's bus signals such as G8PP+68K8, it definitely not "designed for RC2014", even though in all cases it uses RC2014 physical connector.
https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:g8pp:g8ppbase68k8

These are my trial balloons, I like to know what people think.

  Bill

[Bill Shen]

I didn't mention the several plain vanilla motherboards with Z80 and multiple 40-pin RC2014 expansion connectors (K80, Simple80, Z80MB64), but I assume they all qualify as "design for RC2014".
  Bill

[Steve Cousins]

Bill,

I think your assessment is correct. 

All your "designed for RC2014" have a compatible bus connector and work with a reasonable range of official RC2014 modules.

I don't read anything into Spencer's description that says a module must use external memory from a different module on the RC2014 bus. So only supporting I/O modules seems fine to me.

I'm not sure about the G8PP. I don't think the use of the "Spare" (USER) pins in itself invalidates the design. 

I think my SC111 Z180 CPU module and SC119 1MB memory module, may not be considered "designed for RC2014" as they rely on A16 to A19 being on the bus. That is why I'm trying to establish if Spencer's guidance, from last year, on these pin designations is part of the RC2014 spec. If I made a single module containing the CPU and the memory, then it would qualify, I believe, as it would run on any RC2014 backplane and work with a reasonable range of official RC2014 modules. If I mounted the two modules on a mini backplane and plugged that into an RC2014 backplane, again it would become compatible. Bulletproof definitions of compatibility aren't as easy as they sound.

Steve

[Alan Cox]

> I think my SC111 Z180 CPU module and SC119 1MB memory module, may not be considered "designed for RC2014" as they rely on A16 to A19 being on the bus.

But you can plug the CPU card into a true RC2014 bus and use it as a
faster CPU for ROMWBW ?

Some of the other CPU types are interesting questions though. The 8085
board works with a lot of RC2014 cards but doesn't generate an M1
signal so doesn't work with a few third party boards (anything using a
Z80 CTC or Z80 PIO in interrupt modes). Right now I'm running the 8085
board with 512K ROM/RAM, CF adapter, 16550A UART and once I get time
I'll get the Z80SIO and TMS9918A bits sorted out.

Similarly the 6502 board although I'm still experimenting to see how
compatible it is.

IMHO user pins shouldn't be an issue providing they have jumpers.

Alan

[jopil]

Hello all.

Guys, the issue turns to be and seems like becoming a political like issue. Spencer has been very clear on what the "RC2014-Z80" forum has been and it is about. However, the core engine for the health, the vigor and the prosperity of a community, of any kind, is evolution. No evolution -> Death. Spencer, although has created a small revolution, along with all makers of all kinds, here, needs I think, to move to a SUB-THREADing of the main "RC2014-Z80" forum. That way all opinions would be better classified and expressed in certain categories and novices, along experienced users/developers, would have the opportunity to focus on their specific domains of interest in a much better and productive manner. We do not re-invent the wheel here, we just make it available to as many new explores and inquiring minds as possible. In that respect I would suggest that this forum could be for example sub-divided in sub-forums with titles like:

RC-2014 100% Compatible Backplanes

RC-2014 100% Compatible Backplane Variants

RC-2014 100% Compatible CPUs

RC-2014 100% Compatible Boards

RC-2014 Firmware

RC-2014-Utils

RC-2014-Applications

RC-2014 Backplane Extesnions

RC-2014 Backplane Evolution

RC-2014 xBoards (For Backplane Extensions)

Rc-2014 xCPUs (For both BPx & BP Evolution)

and also in some few other sub-threads with names/titles inspired by the very innovative thinking of the members here. I'm doing Cortex-ARMs, ML and lately RISC-V for living, but this forum here is one of a kind. Makes us all to not only re-focus to the, YET not fully explored, powers of the origins of the information/computers revolution, but also to help many new citizens and kids into becoming aware of the time/technology line and power of one of the first very important factors in that evolution/revolution process, namely Z80 + family.

John     

[Steve Cousins]

I really like this forum. It is friendly, entertaining, educational, active, and got some great members. Whenever I fancy a break I can drop in here and there is usually something being discussed.

However, I would like to broaden my activities into areas not really appropriate to "RC2014-Z80". Can anyone suggest a good place to hang out?

Steve

[Alan Cox]

On Wed, 19 Jun 2019, 10:32 Steve Cousins, <steve...@gmail.com> wrote:

I really like this forum. It is friendly, entertaining, educational, active, and got some great members. Whenever I fancy a break I can drop in here and there is usually something being discussed.

However, I would like to broaden my activities into areas not really appropriate to "RC2014-Z80". Can anyone suggest a good place to hang out?

retrobrewcomputers.org is where a lot of stuff happens and the ECB folk hang out.

vcfed has lots of stuff but the focus is on vintage machines extending to things like new cards and replicas rather than new systems

Alan

[Bill Shen]

I'd echo Alan's recommendation of retrobrewcomputers.org, but it is pretty quiet and the system administrator is very busy with his own life such that it can take a month to get registered.  vcfed is a good example of splitting the general interest into many sub topics.
  Bill

On Wednesday, June 19, 2019 at 5:02:58 AM UTC-6, Alan Cox wrote:

[Nigel Kendrick]

Ditto - was going to mention Retrobrew (ditto also that it's not the most active of places at times).

I have found a few useful/interesting things via following the right people on Twitter, and hackaday.io sometimes has a decent article/write-up (among the less complete stuff).

-- Nigel

[Richard Deane]

I'm not sure whether it is because I am a newbie on vcfed but my posts only show after almost a day's delay for moderation, which is terrible for timely exchange with someone.
Richard (riwide on vcfed)

[Greg Holdren]

Not retro specific but for general Electronics, Microcontroller, test equipment etc there is:

https://www.eevblog.com/forum/index.php

EEVBlog YouTube channel by Dave Jones.

Greg

[Michael Stevens]

I understand Spencer has no real engineering knowledge or lacked sight of how this could be used by others. Not so many ways to wire up a Z80 with memory etc. The clever part is splitting this across many boards for sales. I see he is forgetting many knowledged people sat behind him now. If the real issue is taking food from my table, that seems better actually told.   

Regards

Mike.

[Richard Lewis]

In google groups it is possible to create message categories to group messages according to these categories. Groups also support message tagging but not both at the same time. To test this concept I created a new group which you can check out here: SBC-Z80 t with the following categories (see image). It is also possible to organize the categories into hierarchical groups to keep thing organized. My suggestion for this group would be to add something like the following (see image). Before a message can be posted a group must be selected. The groups are just off the top of my head, suggestions are welcome

-Richard 

 

[Bill Shen]

What I read is the Official RC2014 products will stay modular and simple and remain the same. However, the people designing boards for RC2014 (I count myself as one of them) are free to use the existing RC2014 form and fit and take advantage of existing boards and be part of the RC2014 ecosystem. Spencer has very generously lend the RC2014 brand to third party designs which are widely sold on Tindie next to his official RC2014 products and established a forum for users that is responsive to questions and tolerant of the occasional flaming. I have not read any restriction to RC2014 add-on or clone, just there won't be any guidance, for or against, regarding the proposed extension to existing RC2014 bus. We are free to design away, like we've always done, but there no assurance our products will be supported in future official RC2014 products. This has been the case all along except it is official now. I'm grateful of Spencer's generosity and thank him for his openness and tolerances.
Bill

[Richard Deane]

I concur with Bill and after building a zeta2
and having a brick (in no way Sergey's fault), I ventured into rc2014, building a working system and venturing into more rc2014, then a few outside, eventually getting my zeta2 sbc working. I couldn't have done that without the friendly help of this group, and in return on the few and rare occasions that I can contribute to help others I do.

I do not appreciate some contributors with strongly negative views and knocking others at a personal level, and hope that they will just quietly take a hint and drop out of this group. It is after all a group founded by Spencer to support RC2014.

Thank you to all the supporters, I won't be naming them as I would be forgetting someone important, but thanks to all designers enhancing rc2014.

Just wish we had some case designers on Tindie :)
Richard

[Tim Hardy]

I don’t contribute much or often to this group but I feel obliged to
stand up and say I agree with Bill and Richard.

There’s an unpleasant tone to some of the contributions to this
thread. To an extent I understand that the topic was started with some
unfortunately provocative language but ultimately this is Spencer’s
group and Spencer’s product and he has the right to define what that
is.

Attacks on his engineering skills or the fact that he makes a living out
of doing this are out of line.

I think it would be a huge shame if this group fragmented. I would love
to see a way that those who have graduated from the basics and are now
pushing the boundaries of what is possible could be given a space to
continue without having to go elsewhere. I learn from all of you.

I am certain a solution can be found - attacks on one another however
make that less likely to occur.

> --
> You received this message because you are subscribed to the Google
> Groups "RC2014-Z80" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to rc2014-z80+...@googlegroups.com.

> To post to this group, send an email to rc201...@googlegroups.com.

> To view this discussion on the web, visit

> https://groups.google.com/d/msgid/rc2014-z80/7bf65802-6d05-41ff-b7f9-2da642474a23%40googlegroups.com.

[Steve Cousins]

Over the last few days, I've given quite a bit of thought to what has been said on this topic.

It is perfectly reasonable for Spencer to:

* limit the RC2014 to "a simple 8 bit Z80 based modular computer"

* limit what is discussed in the "RC2014-Z80" group.

* have a trademark to help protect his business.

The problem now is that much of what is discussed in this group does not fit within the description: "a simple 8 bit Z80 based modular computer" or is not strictly 100% compatible with the RC2014 (creating potential issues with the trademark).

Spencer has made it clear that the RC2014 will remain "a simple 8 bit Z80 based modular computer", while many of us who are no longer new users want to move beyond that and, in some cases, beyond the current official Standard/Pro RC2014 bus. Any potential new user reading this forum could well get the impression the RC2014 is NOT "simple".

I really like the RC2014 community but feel the best solution is to create a new forum (an RC+ group, if you like) for people to migrate to as they move beyond Spencer's RC2014. This will leave the main RC2014-RC group to focus on Spencer's stated goals, whilst providing a way forward for those who have invested in the RC2014 standard. The new forum could also be open to other standards, not just supersets of the RC2014.

If there were two groups I would anticipate being active in both. If they were both google groups they can co-exist well within a browser tab so there is not much of a disadvantage in the split.

Steve

[jopil]

That's a good and well put idea Steve. Suggested names also could be RC2019x, RC2020x. Are you considering creating such a group?

John

[Tadeusz Pycio]

I am sadly reading this declaration of disagreement with the use of other solutions that deviate from the original concept of RC2014. I treated this platform as a great and cheap base for developing new solutions limited only by the possibilities of the adopted bus. Thank you Sencer, for the effort you put into the development of this platform, but there are also those who are looking for new challenges. I am currently working on a Z8000 system cooperating with Z280 on the extended RC2014 bus, not in the pursuit of MIPS only for my own pleasure and creation fun. Yes, it will not be a classic RC2014, but it will be created thanks to your idea.

[Alan Cox]

> I really like the RC2014 community but feel the best solution is to create a new forum (an RC+ group, if you like) for people to migrate to as they move beyond Spencer's RC2014. This will leave the main RC2014-RC group to focus on Spencer's stated goals, whilst providing a way forward for those who have invested in the RC2014 standard. The new forum could also be open to other standards, not just supersets of the RC2014.

Sounds a good plan to me. Count me in. I'm having lots of run with
RC2014 and 8085 processors 8)

Alan

[Richard Lewis]

Hi Alan, head over to: sbc-z80, it's a WIP and some of us are collaborating on the forum structure. If you would like to contribute let me know 

[Richard Lewis]

Please have a look at: sbc-z80

[Greg Holdren]

Alan and Jopil,

Richard Lewis has created a group here:

https://groups.google.com/forum/#!forum/sbc-z80

Greg

On Wednesday, June 19, 2019 at 5:05:53 PM UTC-7, Alan Cox wrote:

[Steve Markowski]

On Sunday, June 16, 2019 at 3:39:20 PM UTC-4, Spencer Owen wrote:

The RC2014 was never designed to run super fast CPUs with a huge range of exotic peripherals and loads of memory.  It was designed to be simple.  Simple to build, simple to understand, and simple to program. . . 

Well, my grandson and daughter have moved out, the summer reunion on Long Island is over, so I thought I would tip my toes back into the RC2014 pool.  Wow, the water has gotten hot.  It seems I have missed some heated discussions.

Spencer is right.  The RC2014 is a beginners bus which does not support big memory, DMA, multiple CPUs, or high speed serial I/O.  Instead, it supports novices.  Indeed, after my several year absence, I am relieved to see that the bus hasn't changed.  Thank you Spencer.  This means I can pick up exactly where I left off.  

My Zorak motherboard has some slots that use crossover bus lines.  My intent is to play with DMA and to home brew some interrupt acknowledge hardware.  This is beyond Spencer's intention of the spec.  Nevertheless, these special slots are RC2014 compliant on pins 1-37 and this helps nail down all the other stuff and leave the door partway open for RC2014 spec boards.

Other slots on my motherboard are fully RC2014 compliant and I hope to be able to run most all of the standard RC2014 boards.  

Stick to your guns Spencer! 

BTW, there is already an expanded bus spec, yes?  I am using it for needed DMA signals.

[Mark T]

Why is membership required to view the new group? It seems that might discourage some from reviewing the content before joining the group.

Mark

[Richard Lewis]

Hi Mark,

Sorry, still learning the admin features . It is now set for "anyone" to be able to join. Please feel free to check it out: https://groups.google.com/forum/#!forum/sbc-z80

In order to post will need to request permission

-Richard

[Michael Stevens]

@Tim Hardy

Respectfully I disagree with your statement which I presume was directed at me. I stand by both statements.

He has taken a previous design and split it up across multiple boards. He sells them and as far as aware is his personal business. 

Really is little engineering skills to do so. 

So how my comments are out of line you can expand on this now if you so wish?

Regards

Mike.

Virus-free. www.avast.com

To view this discussion on the web, visit https://groups.google.com/d/msgid/rc2014-z80/8AB769D6-6C3A-4283-885F-ED4102ABB4C7%40filteracy.com.

[Tim Hardy]

@Mike

I am really not interested in having a fight. I have nothing further to add.

To post to this group, send email to rc201...@googlegroups.com.
To view this discussion on the web, visit https://groups.google.com/d/msgid/rc2014-z80/CANDE_bmM6K17H-HEztYr5H3s5-mguwD2-nLZwD2gAHUWpxThgA%40mail.gmail.com.

[Michael Stevens]

@Tim Hardy,

Fight, never saw a fight. I think you will come to understand what I have said is actually correct. 

Virus-free. www.avast.com

To view this discussion on the web, visit https://groups.google.com/d/msgid/rc2014-z80/A3433B5E-46AA-4D74-862F-1F9E25D82BF4%40filteracy.com.

[Tom Storey]

On Thursday, June 20, 2019 at 4:20:13 PM UTC+1, Richard Lewis wrote:

Hi Mark,

Sorry, still learning the admin features . It is now set for "anyone" to be able to join. Please feel free to check it out: https://groups.google.com/forum/#!forum/sbc-z80

In order to post will need to request permission

-Richard

I am unable to access the group. I get a mesasge saying to contact the owner, but how can I when I cant even view the group and it doesnt tell me who the owner is or how to contact them. :-) 

[MyklHn]

The group was changed to retro-comp. an email was attempted to be sent out to everyone.

https://groups.google.com/forum/m/#!forum/retro-comp

Michael

[Don Prefontaine]

Derry

Rather than spend 3 years googling "Teensy running emulated CPM", do you have a handy link(s) you'd care to share? Thanks. Don.

On Sunday, June 16, 2019 at 5:50:29 PM UTC-4, Derry UK wrote:

There is more than one way to skin a cat. That is why I have a dozen or so z80 systems. Th Rc2014 wasn't one of my favourites but I liked the idea of plug in boards and so do a lot of people it seems.

I am now at my happiest with a Teensy running emulated CPM. The DOS formatted SD card makes life a breeze but more importantly it allows me to write Z80 assembler all day long.

Derry.

PS I will get that text editor finished one day ....

PPS I don't read a Teensy forum for my Z80 fix I read this one.

[Derry UK]

It is https://github.com/MockbaTheBorg/RunCPM/