New modules

[Tadeusz Pycio]

designed new serial transmission modules, one universal for all Z80 SIO models and another for 16C450/550 chips.

[Tadeusz Pycio]

Another module is a Z180 MPU with 128kB memories each being prepared for the role of CP/NET network server, running under MP/M. I am in the process of writing system software under this specific module. I do not envisage working directly on it, so this amount of memory is completely sufficient.

[Tadeusz Pycio]

"640kb is enough for anyone" ;-)  The first steps for x86 adaptation on RC2014 have been made. Universal linear memory module for Z180/280 and V40 processors built. Now it is time to design a board for the V40 NEC processor.

[Chris Odorjan]

On Friday, 11 November 2022 at 08:57:58 UTC-5 Tadeusz Pycio wrote:

Now it is time to design a board for the V40 NEC processor.

Nice! I bought a handful of V40HLs off eBay a few years ago with the intent on doing something for RC2014 or an ISA SBC with them, but I keep distracting myself with other things :-P

(From what I can tell the HL is pin compatible but can also emulate an 8237 DMA controller)

[Alan Cox]

On Fri, 11 Nov 2022 at 15:10, Chris Odorjan <codo...@gmail.com> wrote:
>
> On Friday, 11 November 2022 at 08:57:58 UTC-5 Tadeusz Pycio wrote:
>>
>> Now it is time to design a board for the V40 NEC processor.

Nice CPU. I went with the 80C188 for my RC2014 8086 CPU card because I
could get them easily.

[Colin MacArthur]

I just ordered my V40 boards today.

https://oshwlab.com/cmacarthur/v40-sbc

https://oshwlab.com/cmacarthur/v40-mem

https://oshwlab.com/cmacarthur/v40-sbc-kbd

Not sure if they work !

FYI 
v40-sbc-kbd card has a "Port B"  for future PCXT use...

CM

[Tadeusz Pycio]

v40-sbc-kbd card has a "Port B"  for future PCXT use...

I see you are planning a more ambitious project. I wanted to limit mine to just CP/M 2.2 in 8080 emulation mode and CP/M86.

[Colin MacArthur]

I think CP/M 2.2 in 8080 emulation mode and CP/M86 would be a GREAT start...

I want to PLAY with the v40 and PS/2 KB controller, I/O ports & RTC just for fun  (NVRAM storage).

Because I have more tools etc for working with RC2014 like 80 pin.

FYI

If you haven't already you may want to checkout https://j4f.info/v20-mbc.

Tons of info on getting v20 working (v20 is the core of the v40)

CP/M-80 & CP/M-86

also

MSDOS 2.2  https://github.com/keyvin/v20mbc-msdos

FREEDOS     https://github.com/wenij/v20_mbc_freedos

CBIOS           https://github.com/binaryspider/v20-mbc_cpm8680_cbios

CM

[Tadeusz Pycio]

Another module, this time I2C with built-in RTC and EEPROM. The connector is compatible with the SC137 and has the possibility of direct connection of an OLED display.

[Bill Shen]

Nice looking board.

Some OLDE display has different VCC/GND pin out where VCC is the outside pin and GND is inside.  For my OLED display connector I designed in jumpers that can swap the VCC and GND pins.

Do you have software that can drive the OLED through PCF8584?  I'm curios how quickly the screen can be refreshed with PCF8584 compare to bit-bang I2C protocol.
  Bill

[Tadeusz Pycio]

Hi Bill,

I have not yet written new software for this module. The main purpose of this module was the RTC and the contained battery-backed memory to store the network card configuration, but I will also check this OLED display. Once the software is ready, we need to set up a test for this display.

[Steve Crompton]

Hi there,

Cool - nice job

What is the maximum clock rate for I2C protocol - 400-500 KHz ?? ..... and can this chip/card support the maximum rate?

I understand the SPI protocol supports faster clock rates (MHz) but don't know of a true parallel to SPI interface chip - anyone?

I2C is perfect for low speed devices, SPI would be advantageous to support larger displays though - and this is something that interests me

Anyone implemented parallel to SPI in CPLD ?

Non the less nice card and very useful and I will be interested to see how much of a speed advantage there is using this chip over a bit banged 12C interface

Steve

[Ed Porter]

On 24/11/2022 10:21, Steve Crompton wrote:

> Anyone implemented parallel to SPI in CPLD ?

SPI is pretty straightforward. Here's one implementation:
https://forum.digikey.com/t/spi-master-vhdl/12717

-ed

[Tadeusz Pycio]

I don't think there will be any significant differences, the PCF8584 works up to 100kHz and here it will be a bit slower due to the 7.37MHz clock instead of 8MHz. The only thing more convenient is the software and hardware support for the protocol.

[Phillip Stevens]

Tadeusz wrote:

I have not yet written new software for this module. Once the software is ready, we need to set up a test for this display.

For what it is worth, I've some code for the quite similar PCA9665 device and for its I2C protocol handling.

It might be useful for you have a look at to see if anything is reusable.

The key feature is support of interrupt response mapping, so that the status register with I2C state controls which I2C message is returned, taking the I2C protocol management out of the foreground. It works for burst transmit and receive mode too, so entire I2C sentences can be exchanged under interrupt control.

Cheers, Phillip

[Bill Shen]

Software support is worth it.  I believe ROMWBW will support DS1302 RTC connected to PCF8584, although I have not tried it, yet.

I was able to run BadApple! on 128x64 OLED at 20 frames/sec by bit banging which is close to 200Kb/s, but I "cheated" by overclock Z80 to 25MHz.
  Bill

[Tadeusz Pycio]

Software support is worth it.  I believe ROMWBW will support DS1302 RTC connected to PCF8584, although I have not tried it, yet.

I don't think the 3-Wire Interface device (DS1302) is properly supported by the I2C controller (PCF8584). I used a dedicated RTC chip for I2C - the DS1307.

I was able to run BadApple! on 128x64 OLED at 20 frames/sec by bit banging which is close to 200Kb/s, but I "cheated" by overclock Z80 to 25MHz.

 I doubt that the PCF8584 will match this performance, for display support a better option would be to use the PCA9665 (transfer up to 1MHz) or PCA9564 (400kHz).

[Alan Cox]

> I doubt that the PCF8584 will match this performance, for display support a better option would be to use the PCA9665 (transfer up to 1MHz) or PCA9564 (400kHz).

You can bitbang at the PCF8584 speed. The 8584 doesn't really help
unless you have something meaningful else to do between the bits (like
say receive serial data - and that can be done with suitably crazy
code). I did build an 8584 card and as well as the chip being
basically unobtainium, haven't really seen the point of it over some
PIO bits and a couple of diodes.


Alan

[Tadeusz Pycio]

Hi Alan,

I2C was intended to handle slow devices; SPI is used for faster ones. On the other side of the coin, retro processors don't have that much in the way of processing power to pass up the opportunity to use the hardware for such tasks. The PCF8584 is perfect for this if high transfers are not expected. Added to this is the simplicity of the software.

[Bill Shen]

I'm getting forgetful, now I've recalled previous conversation about PCF8584 being under-powered. sigh...

I went looking for the design file of RC2014-DS1302 and found it on github.  This is the first time I actually looked at the schematic and now realize it does not involve PCF8584 at all.  It is basically a bit-bang I2C interface.

I was looking for a SIO2 prototype board and found it alread had a PCF8584 prototyped as well.  I will add a DS1307 to it.  I added an eBay RTC mini board and implemented the logic described in RC2014-DS1302 schematic in CPLD.  ROBWBW is able to find it.  I used Zsystem's RTC to set the clock so now ROMWBW is displaying the time correctly.  This is kinda fun--going off on a tangent because of a misconception, found the right information, prototyped the right design, and have it validated on real platform, all on a Thanksgiving morning when I really should be helping out in the kitchen!
  Bill

[Alan Cox]

On Thu, 24 Nov 2022 at 19:16, Bill Shen <coinst...@gmail.com> wrote:
>
> I'm getting forgetful, now I've recalled previous conversation about PCF8584 being under-powered. sigh...
>
> I went looking for the design file of RC2014-DS1302 and found it on github. This is the first time I actually looked at the schematic and now realize it does not involve PCF8584 at all. It is basically a bit-bang I2C interface.

Not even that the 1302 is simpler than even I2C

>
> I was looking for a SIO2 prototype board and found it alread had a PCF8584 prototyped as well. I will add a DS1307 to it.

You can bitbang a 1302 off the spare SIO2 modem lines if you want to
be truly evil

Alan

[Greg Holdren]

65SPI is for the 6502 bus but the interface could be changed to work with Z80/Intel like interface I'm guessing.

https://sbc.rictor.org/65spi2.html

Greg

On Thursday, November 24, 2022 at 1:21:04 AM UTC-8 Steve Crompton wrote:

Anyone implemented parallel to SPI in CPLD ?