New YAZ180 PCBs

[Phillip Stevens]

There's been a bit of interest in "flat" SBC Z80 machines lately, so I thought it was worth noting that I've just received the second batch of YAZ180 PCBs (Version 2.4), and put them up on Tindie.

I've already made (and sold) a few of these V2.4 boards, and I don't have any remaining errata.

Here's the YAZ180 github link if you're interested, and want to read more.

Essentially it is: CPU Z8S180 Z180 at 36.864MHz, APU Am9511A-1, IDE, I2C, and "WiFi" via ESP8266.

Top of mind for me now is to get the device drivers for the two I2C devices working.

The PCA9665 has an internal 68 Byte buffer, so it can send or receive a whole I2C sentence on one interrupt (when I get the code working, of course)...

Cheers, Phillip

[Steve Cousins]

Hi Phillip

Good to see the latest YAZ180 on Tindie and on the first screen of popular products for a while too. 

For anyone not familiar with the YAZ180: It is a high performance, sophisticated and mature Z180 based design. 

YAZ180 on Tindie:

https://www.tindie.com/products/feilipu/yaz180-modern-single-board-z80-computer/

It is good to see demand at both ends of the Z180 motherboard range (both price and sophistication). Plenty of room for all different approaches I think.

Steve

[Phillip Stevens]

Steve Cousins wrote:

Good to see the latest YAZ180 on Tindie and on the first screen of popular products for a while too.

That was a pleasant surprise to hear.

For anyone not familiar with the YAZ180: It is a high performance, sophisticated and mature Z180 based design.

I'll take "mature" as a big compliment, from one old grey to another. :-)

 

It is good to see demand at both ends of the Z180 motherboard range (both price and sophistication). Plenty of room for all different approaches I think.

I would love to do a kit for the YAZ180 too, but frankly I can't justify holding stock of the components to make kits.

The BOM at Digikey comes in at just under AUD200 for one board, and that's without the Am9511A-1 or TIL-311 devices.

And with tax and shipping from Australia it just isn't worth the trouble.

I do have quite a few of the Am9511A-1 and TIL-311 devices around though. I've thought about just adding those as an option to the PCB page, but not sure how much interest there would be.

Cheers, Phillip

[Steve Cousins]

Yes, supplying kits is harder and more costly than is obvious. 

A little rant about kits for anyone who is bored:

I've got lots of stock of most things now but I still keep making mistakes and running out of others. 

Just storing 50 of an item is not compatible with my 'personal use' storage systems. I've had to set up more storage and now have a space problem.

Local tax and import charges are a pain too. When I order a few bits and pieces from China they turn up with no customs charges. When I order 50 I often get a small customs charge plus an annoying large handling charge. I find myself having to buy in small quantities and repeat the orders regularly. 

Many of the 'special' parts, such as USB adapters, are only attractively priced from suppliers who have 5 in stock. I then end up placing multiple orders with different suppliers. Then when the parts turn up there is never any paperwork so I don't know which supplier they came from.

Rant mode OFF

On the plus side, I can, in theory, make some pocket money and it is very rewarding having someone willing to pay for something you have created.

I think I'll stick with designs that can be at prices most people can justify for hobby use. I'll probably stick to my current rules about 0.1" pitch through-hole components for reliable assembly by most makers. I'll also try to generally keep to the 1980s technology look and feel, where possible.

Many more ideas in the pipeline :)

It's a great hobby.

Steve

[Bill Shen]

Getting a project from lab to production line is difficult and under appreciated.  I worked in hardware side for my entire working career and I have the greatest appreciation for the Industrial Engineer (I'm Electrical Engineering by training).  They have to be jack-of-all-trades and work with people from all walk of life and get paid the lowest among the engineering profession.  This is probably why most engineers want to be the designers instead of producers because it is easier and get paid more.

Because it is not easy, I am not actively selling.  However, it is rewarding to see my design being used and I do learn much from user feedback, so I make a point of putting one product out on USA eBay but at my own pace of one board per week.  I also use the auction format and start from 99 cents to measure demands of the retrocomputer market.  There is one on eBay right now, it is the 23rd board:
https://www.ebay.com/itm/303257347014

  Bill

[Richard Lewis]

For myself I have no intention of selling anything I create. I will however make my projects freely available on Github. Maybe I'll sell spare boards like Steve's "pick and mix" category on Tindie. But with a disclaimer that "you are on your own...". 

Because:

1. I just don't like through-hole parts anymore. Just so inconvenient to solder; hate bending leads on resistors and then having to clip them. I can drag solder a 144 pin QFP in seconds. Also passives down to 0402 are not a problem for me to hand solder. Besides, I use a reflow oven and paste anyway and only use a hand iron for touch-ups.  
2. I barely have time (like no more than 1-2 hrs per day) to put even one board together. Can't imagine having to build and post 5-10 boards at a time (assuming my board is somehow popular).
3. Don't have the time to help people debug if something goes wrong. Seems people are having enough problems with THT already (which should be foolproof). SMD is too scary for most casual hobbyists. 
4. I would never sell a kit to someone without first providing full documentation with build guides, parts lists and troubleshooting guides. It's just not in my psyche.  I wouldn't be able to sleep at night knowing that someone paid money for my kit and wasn't successful because of no or misleading docs....
5. Any negative reviews would stress me out. 

Anyway, think I'll build a YAZ180 since I have about 20 TIL311 display chips that are not being used. 

-Richard

[Richard Lewis]

Hi Bill,

I noticed on your boards that your traces turn at 90 deg angles. As I was learning how to make PCB's, various youtube videos and forums were advising me that 90deg and very acute angles were bad but never gave a good explanation as to why (acid traps?). There was a recent article in Hackaday: WHAT’S THE DEAL WITH SQUARE TRACES ON PCBS that debunks the myth that 90 degree traces are bad. 

Seems the only issue that one must contend with is an increase in trace capacitance but then that only becomes an issue at extremely high frequencies. I'm using 45deg turns because it looks more aesthetically pleasing. So I guess in summary that right angles being bad is a myth. 

-Richard

[Bill Shen]

Richard,
Retrocomputers of 1970's and 80's have relatively slow rise & fall time so right angle PC traces are not an issue. I'm not even worry about power/ground planes, controlled impedance, or matched trace length, so rounded corner to avoid reflection and radiating are least of my concerns.  In fact, our boards should work just fine without any bypass capacitors--this is how slow our systems are.  This is the reason I uses my 20+ year autorouter 95% of the time and don't worry much about trace length, reflection and cross talk.  I do have to be careful around the compact flash interface because it is a fairly modern device.
  Bill

[Phillip Stevens]

Richard Lewis wrote:

For myself I have no intention of selling anything I create. I will however make my projects freely available on Github. Maybe I'll sell spare boards like Steve's "pick and mix" category on Tindie. But with a disclaimer that "you are on your own...".

My personal hardware journey started because I couldn't design hardware, so bribing someone who could was the only way to get what I wanted to have. Essentially, I ran a crowdfunding campaign to convince a hardware capable friend that there was a market for what I wanted to own. When the campaign was successful, we (he) had to deliver for all of us.

Later, when I wanted something else, I started to learn the ropes of hardware design, but again used crowdfunding as a litmus test of interest.

The YAZ180 is a personal journey. It started off as "what would an Arduino from the 1980s look like?".

Then, it became more specific when I learned more about the history of the Am9511A APU. "Just how fast is a 1970s APU/FPU, that was used to calculate atomic reactor management, and ICBM / rocket flight paths?". In fact the APU arc has been the one thing tying the last few years of my work together. The final two pieces were writing a z180 and z80n (Spectrum Next) floating point C library with IEEE 32-bit floats (same as the Am9511A), and then (next) integrating the APU float format into the same platform, to test the performance 1:1. Perhaps by early next year it will be done.

 

Because:

• I just don't like through-hole parts anymore. Just so inconvenient to solder; hate bending leads on resistors and then having to clip them. I can drag solder a 144 pin QFP in seconds. Also passives down to 0402 are not a problem for me to hand solder. Besides, I use a reflow oven and paste anyway and only use a hand iron for touch-ups.

For me, it was the space issue. It wasn't possible to get everything into a 160mm x 100mm board.

• I would never sell a kit to someone without first providing full documentation with build guides, parts lists and troubleshooting guides. It's just not in my psyche.  I wouldn't be able to sleep at night knowing that someone paid money for my kit and wasn't successful because of no or misleading docs....

For the last version of the YAZ180 PCB v2.1 there were a few errata that needed to be fixed by hand cutting traces. It stressed me out so much that I always included an extra PCB in orders (silently), because I couldn't handle it if someone broke their board, and didn't have a spare.

Now the v2.4 doesn't have any issues to my knowledge, so I'm more comfortable with the boards and documentation level.

Cheers, Phillip

[Mark T]

Great now I need to try curved traces in eagle, as if I don’t have too many ideas to try already :)

Used to layout boards x1 or x2 size with black crepe tape on clear acetate. Always amusing when someone took out a design they made a couple of months ago to make a slight mod only to find they stretched the tape too much and all the traces were now touching. I used to use straight line with 45 degree cuts instead.

Mark

[Alan Cox]

> I've got lots of stock of most things now but I still keep making mistakes and running out of others.

I've been doing this for model railway kits for a decade hence the Etched Pixels.

It doesn't improve, even when you think you've got it lined up beautifully
suddenly everyone orders the same obscure items, or you run out of
something you missed (like packing boxes)

> Many of the 'special' parts, such as USB adapters, are only attractively priced from suppliers who have 5 in stock. I then end up placing multiple orders with different suppliers. Then when the parts turn up there is never any paperwork so I don't know which supplier they came from.

It is worth talking to some of them directly, or dealing with Alibaba.
There are people in Shenzen and HK who will go out and get and pack
whatever you want in whatever size bundles you want (and quite often
write whatever you ask on the customs form - but that's not a good
idea!).

> On the plus side, I can, in theory, make some pocket money and it is very rewarding having someone willing to pay for something you have created.

It's even more fun when you do it enough to count as a business. Then
you have stock and accounts to do 8)

> I think I'll stick with designs that can be at prices most people can justify for hobby use. I'll probably stick to my current rules about 0.1" pitch through-hole components for reliable assembly by most makers. I'll also try to generally keep to the 1980s technology look and feel, where possible.

Oh good - I can't even seen some of the dandruff people use as
capacitors and resistors 8)

> Many more ideas in the pipeline :)
>
> It's a great hobby.

Yep. I've been putting together a rework of Ben's 8085 board to fix
the IRQ issue, but there was this spare bit of board left over so I've
also added a simple MMU that allows it to run with a flat 512K/512K
memory card (I hope), as I have one spare right now.

Waiting the keyboard and 82C54 boards back. If they 82C54 one works
then I've got a revised version with its own crystal and more sensible
chaining of stuff. That also had some space on it so it's got a
totally unrelated MAX232 serial on it so I can turn the tx/rx lines on
the backplane into a proper 9 pin socket.

The other bits I've got done I think  (80C88, 80C188, slave Z80 -
loosely based on an old S100 design, quad uart/timer) I will wait
until I see how well I'm doing on the simpler sutff 8)

Given the comments about low speeds and slack, is it still worth
stitching ground planes on boards - and if I try and go to 14MHz
65C816 with 74AC series chips one day (not in a hurry!) then do I need
to care more about layout ?

Alan (sorry accidentally sent this direct to Steve first time)

[Phillip Stevens]

Alan Cox wrote:

Given the comments about low speeds and slack, is it still worth

stitching ground planes on boards - and if I try and go to 14MHz
65C816 with 74AC series chips one day (not in a hurry!) then do I need
to care more about layout ?

(Noting: certainly not an expert).  I think it is worth getting a good ground plane.

On my last project, I was trying to produce quiet (in the analogue sense) output from an ATmega1284p (in an Arduino clone). By quiet I mean less than 1mV of noise on the output for 12 bits resolution. The fact that the power supply was generating more than 12mV of noise on the 5V supply didn't help matters at all.

Putting a bit of thought into separating the power from analogue parts of the (tiny Uno sized) PCB helped, as did making the board 4 layer to provide a solid (segmented) ground plane.

I've become a bit OCD about the whole groundplane thing since then, and got quite paranoid when I had to use the ground plane (green on the right) to route the IDE pins for YAZ180. I only justified it because there was no other way, and the issue was localised on a small part of the board, where there were no currents flowing.

More generally to comments on routing ...

I tried to capture the "flow" of signals around the board anti-clockwise with address on the back, and data on the front. Initially, I also tried to make large "retro" swooping corner curves, but then ran out of space and had to tighten everything up. I'm still preferring curves to corners (90deg or 45deg). Just because it suits an aesthetic.

This screen capture is a bit miss-leading, because the GND (green) and 5V (grey) are actually flood filled. The 12V and 3V3 lines are shown in grey, but the rest of that layer is 5V. There are also some thin stitching in grey and green to help where the flood fill will not go between pins automatically, such as under the bigger devices.

The biggest Ah-ha moment was fighting to route the address lines to the SMD RAM. Getting all the signals to line up was really hard. And the realisation that RAM doesn't need to have linear addressing, allowed me to just attach whichever z180 address line that was handy to the RAM address line was a revelation. It only needs a 1:1 mapping. Everything else is, well, random access.

Cheers, Phillip

[Greg Holdren]

I try to design board as if I were doing some higher speed designs at work even though the parts are slower in Fmax, Trise, TfalI. Just fells more natural to me. Clocks/Diff pairs first, Cap placement, termination (series) resistors, signal routing etc. as well as a good power fill and filtering where possible for a 2 sided board. I do the best I can without busting out the tools like at work designing for SI (Signal Integrity). One can actually model multi PCB interconnected circuits with tools like Mentor Graphics Hyperlynx. Everything is modeled: PCB, connector characteristics and IC characteristics with IBIS files. A lot is common sense if you understand electronic and the rest is intuition/experience. Usually get there 80%-90% off the bat and using the SI tools the rest of the way. Not all boards need SI tools. I did a RPi3 carrier board that will be used between an elevator controller <=> PC, CAN to Ethernet (RPi3). Not really needed. The CAN diff is forgiving.      

Hyperlynx Example

Phillip, That is a nice looking board layout. Work of art. :)

Greg

[Steve Cousins]

Alan, see below

On Friday, 23 August 2019 00:56:32 UTC+1, Alan Cox wrote:

> I've got lots of stock of most things now but I still keep making mistakes and running out of others.

I've been doing this for model railway kits for a decade hence the Etched Pixels.

It doesn't improve, even when you think you've got it lined up beautifully
suddenly everyone orders the same obscure items, or you run out of
something you missed (like packing boxes)

Well, that's reassuring :(

 

> Many of the 'special' parts, such as USB adapters, are only attractively priced from suppliers who have 5 in stock. I then end up placing multiple orders with different suppliers. Then when the parts turn up there is never any paperwork so I don't know which supplier they came from.

It is worth talking to some of them directly, or dealing with Alibaba.
There are people in Shenzen and HK who will go out and get and pack
whatever you want in whatever size bundles you want (and quite often
write whatever you ask on the customs form - but that's not a good
idea!).

Thanks, I might try the asking bit - not the customs bit. I think I'm at that tricky volume where some of the shipments are valuable enough to get noticed by customs and not big enough the Royal Mail (etc.) handling charges are insignificant.

 

> On the plus side, I can, in theory, make some pocket money and it is very rewarding having someone willing to pay for something you have created.

It's even more fun when you do it enough to count as a business. Then
you have stock and accounts to do 8)

I've been legit from day one. I just tacked the PCB and, later, the kit sales onto what is left of my long term business. Submitting accounts to Mr Taxman is not really any extra work or hassle for me, but the number of small transactions I now have required a different approach to the onces previously used.

 

> I think I'll stick with designs that can be at prices most people can justify for hobby use. I'll probably stick to my current rules about 0.1" pitch through-hole components for reliable assembly by most makers. I'll also try to generally keep to the 1980s technology look and feel, where possible.

Oh good - I can't even seen some of the dandruff people use as
capacitors and resistors 8)

Yes, that is a problem I'm having. I remember when my eyes were plenty good enough to inspect solder joints etc. Now I sometimes even miss soldering a 0.1" pin and only see it when inspecting with a magnifying glass. I guess it only gets worse from here.

 

> Many more ideas in the pipeline :)
>
> It's a great hobby.

Yep. I've been putting together a rework of Ben's 8085 board to fix
the IRQ issue, but there was this spare bit of board left over so I've
also added a simple MMU that allows it to run with a flat 512K/512K
memory card (I hope), as I have one spare right now.

Waiting the keyboard and 82C54 boards back. If they 82C54 one works
then I've got a revised version with its own crystal and more sensible
chaining of stuff. That also had some space on it so it's got a
totally unrelated MAX232 serial on it so I can turn the tx/rx lines on
the backplane into a proper 9 pin socket.

The other bits I've got done I think  (80C88, 80C188, slave Z80 -
loosely based on an old S100 design, quad uart/timer) I will wait
until I see how well I'm doing on the simpler sutff 8)

Given the comments about low speeds and slack, is it still worth
stitching ground planes on boards - and if I try and go to 14MHz
65C816 with 74AC series chips one day (not in a hurry!) then do I need
to care more about layout ?

I think you'd get better advice on those speed related issues from Bill. It's above my pay grade :)

As Greg, I think it was, commented elsewhere it is good to design as if you are pushing the limits then the result should just work. Anyway, I try to do that just because it feels like I'm doing a better job.

I'm seeing more and more comments from you about designing PCBs and getting them fabricated. I tried to warn you, but you didn't listen :)

[Steve Cousins]

Hi Phillip

That is a lovely looking layout. The curves look great. I'll have to try a few sometime.

One bit I notice rang alarm bells: (unless it is covered by the flood fill you mentioned)

When I was a lad I seem to remember it being considered a bad idea to have angles between tracks of less than 90 degrees so the area highlighted looks suspect. I think the idea was it created an acid trap that could allow acid to remain on the board longer than it should - eating away at the copper track. Perhaps acid doesn't do that anymore :)

Steve

[Richard Lewis]

From what I've heard with regard to modern fab houses, it seems the "acid trap" issue is a thing of the past. Even if that is true, the OCD in me prevents me for working with any angle other than 45

[Alan Cox]

On Friday, 23 August 2019 20:51:23 UTC+1, Richard Lewis wrote:

From what I've heard with regard to modern fab houses, it seems the "acid trap" issue is a thing of the past. Even if that is true, the OCD in me prevents me for working with any angle other than 45

There is a fun video tour of JLCPCB here

https://youtu.be/ljOoGyCso8s

[Steve Cousins]

Nice video.

Seeing all the processes makes it even more impressive that the boards are so cheap.

Now we know why we don't suffer from acid traps anymore. Apparently, they now use alkaline, not acid :)

Back in the day, two-layer boards were drilled first. I assume now they make the two-layer boards in the same order as the 4 layer ones they showed but skip the processes related to the extra layers.

I watched carefully but was disappointed not to see one of my boards! 

Steve

[John Kennedy]

I'd love to get into making my own boards. I've built stuff using breadboards and Veroboard (stripboard).

Any advice on how to get started as a newbie?

[Steve Cousins]

Hi John

My advice: It's low cost, so just try it with something simple. 

I wrote a series of posts on my website pitched at encouraging people to have a go at designing their own PCBs:

https://smallcomputercentral.wordpress.com/2019/07/26/design-part-1/

Steve

[Phillip Stevens]

Steve Cousins wrote:

That is a lovely looking layout. The curves look great. I'll have to try a few sometime.

Curves = karma.

One bit I notice rang alarm bells: (unless it is covered by the flood fill you mentioned)

Yes, that's just an artefact of quieting the Electrical Rules Check in Eagle. It moans if the VCC pins aren't connected (before the final flood fill), so I just run around and quieten everything by connecting them up. The same applied on the GND plane.

These are the GND and VCC planes before, and after filling.

There are also some links that don't terminate on pins. I use them because the flood fill can't squeeze between through hole pins, and I like to have the fill complete.

Again, it just helps my karma.

Cheers, Phillip

[Steve Cousins]

That's okay then

[Bill Shen]

Very pretty board.  It is clearly hand routed.  How is Eagle's autorouter, would it autoroute this board successfully?
  Bill

[Phillip Stevens]

Bill Shen wrote:

Very pretty board.  It is clearly hand routed.

How is Eagle's autorouter, would it autoroute this board successfully?

Not so much. Turns into a rats nest because it tries to take the shortest path.

After I've done the schematic, the devices appear on the board window. Then I tend to pick up the devices and rotate and position them until I see a minimum of crossed yellow lines, trying to create a signal flow or bus path around the board. Then the layout fun starts. I could never do this as a real job. I'd be far too slow.

Other things "rules of thumb" I've learned from various papers are:

• that many small vias work as solder heat capillaries for the power supply heat sink. I think this was from a TI paper. Helps to conduct heat to the ground plane on front, back, and to the GND layer where it can spread through the whole board.
• to isolate the ground plane under inductors, so that the magnetic flux doesn't generate voltage swings on the ground plane.
• to tie isolated pieces of top and bottom layers flood fill to GND, so they don't act as resonators and produce RF noise.
• that through-hole sockets can serve double duty as vias between layers, so even in a SMD board a few through-hole sockets are good to have.

I'm sure you have a huge set of "rules of thumb" that would be useful for us all to know.

Cheers, Phillip

[Mark T]

Hi Phillip

You mentioned that eagle generates DRC errors if Vcc or ground are only connected by area fill, but i don’t think I’ve had that problem with eagle. Using 7.6 so maybe its a different version.

I follow similar method with layout of components, find the live update between schematic and layout very useful on dual monitors.

Spent a few hours playing with curved traces. Decided I like to put a radius of 0.025 inch on 10 mil traces 45 degree angles, but only use the other curved trace options when there isn’t enough distance for a 45 degree interconnect. Probably going to add a few hours to future design but I think it gives a better finish than simple 45 degree angles, particularly on connections to vias.

Mark

[Phillip Stevens]

Mark T wrote:

You mentioned that eagle generates DRC errors if Vcc or ground are only connected by area fill, but i don’t think I’ve had that problem with eagle.

I'm using the V6.6 for which I have a perpetual "Hobby" Licence. They stopped offering this $100 option after V6.6, so I've never felt the need to upgrade.

At the time I purchased this licence KiCAD wasn't quite up to the same level, so I felt justified in spending a few dollars for a one time purchase.

The "Hobby" Licence is good for 160mm * 100mm * 4 layer (somewhat coincidentally the same as the YAZ180).

That said, it is the Electrical Rule Check that does the moaning. Currently I have 27 approved electrical warnings approved, relating to un-utilised inputs.

The Design Rules Check is also a bit of a whiner. There are something like 588 approved design rule violations approved. Mainly relating to "keep outs" that I've applied to prevent flood filling, and yet have run a trace through the keep out area.

I think they made a pretty substantial upgrade to routing in v7, so probably they've fixed this issue in the interim.

 

Spent a few hours playing with curved traces. Decided I like to put a radius of 0.025 inch on 10 mil traces 45 degree angles, but only use the other curved trace options when there isn’t enough distance for a 45 degree interconnect. Probably going to add a few hours to future design but I think it gives a better finish than simple 45 degree angles.

I like laying parallel traces, then ripping up the corners and then doing a smooth (variable size) curve joining the two parallel sections.

Electrically totally unnecessary, but it really helps my karma.

Regards, Phillip

[Bill Shen]

I do have a "cheat sheet" of checklist but they are generally tied to the quirks of a particular tool.  This being the slow retro electronics, the layout design rules are more physical than electrical.  I like to route two traces between DIP pads, so I need to size the pad, clearance, trace width accordingly.  I seldom do 'flood' or area fill because my boards are generally dense and the flood function does very little good.  I use autorouter 95% of the time, so it is more about preparing the proper placement for the autorouter to work in.  The autorouter works fast, for 100mmX100mm board, it generally completed in 2 or 3 minutes, so I'd move things around and run the router many times to get the best placement.  I'm mostly concerned with proper power/ground distribution; I would start with a board outline that's 0.1" smaller and create few extra power & ground pads and place them at the edge of the board outline to force the autorouter to connect to these pad.  When the routing is done, I would move the board outline 50mil out each direction and create thick power/ground traces manually to connect to the power & ground pads.  This extra power & ground rings provide better power distribution, not anywhere as good as dedicated power&ground planes, but good enough for the retro technology. 

This probably is the densest 100mmX100mm 2-layer board I've designed recently.  It is an expanded version of Tiny68K.  I needed the second CPLD to add Ethernet interface and SPI/I2C expansion.  The autorouter did everything except few manual routing of the power & ground.
  Bill

[Bill Shen]

This 68030 board may be even denser because you can achieve greater route density with through-hole components and the router can't even finish this board with 20 or so connections that I had to manually wired in.  You can see the power & ground rings at the edge of the board.  In term of retro technology, 68030 is in the gray area; the professional would use power & ground planes and paid some attention to electrical characteristics, especially for signals going to the 16 meg DRAM, but I'm just retired amateur fooling around...

[Chris Odorjan]

On Thursday, 22 August 2019 19:56:32 UTC-4, Alan Cox wrote:

Yep. I've been putting together a rework of Ben's 8085 board to fix

the IRQ issue, but there was this spare bit of board left over so I've
also added a simple MMU that allows it to run with a flat 512K/512K
memory card (I hope), as I have one spare right now.

How are you handling the additional IRQ lines on the 8085? I've got an updated 16550 board (mostly to add RTS/CTS and a MicroSD adapter) prototyped on a breadboard w/SC115 that currently works with RomWBW using interrupt mode 1, but I figure it might be useful to be able to route the interrupt from the UART elsewhere for other setups (especially the 8085). (I was thinking at least USR1, which can be used as an input to a CTC board.)

Thanks,

Chris

[Alan Cox]

At the moment I've got the RC2014 IRQ wired to one of the extra interrupt lines (to avoid the need for intack processing) and the INTR line on the CPU is not used for any interrupt handling. That is how I modified Ben's original 80C85 board to work with interrupts and this seems to work reliably. I'm working on a proper 82C54 board for the timers (Z80 CTC/PIO do not work without a lot of extra magic with 8085).

For now the others are not assigned pins, but that's because I am hoping we will get a final BP80 pin assignment so I know if there is a correct place for them to go or not. Separate interrupts for timer and for time sensitive stuff is a win for 80C85 certainly. For Z80 you've got IM2 except that it's basically unusable on the standard RC2014.

Alan

[Steve Cousins]

Not having an agreement for the BP80 pin assignments is also holding up some of my plans :(

[Richard Lewis]

Need to start a new thread I think, starting to become: TL;DR. Perhaps have another discussion wishlist style then vote on it?

-Richard

[John Kennedy]

Perfect! Thanks Steve!