MECB Z80

[epaell]

Hi All,

Not sure if this is of interest to anyone but I've recently been playing with the Digicool Things MECB (Minimalist Europe Card Bus) system. The original boards were initially Motorola focussed (6809) but later expanded to include the 6502 processor card. More recently I made a 6800, 68008 and 8088 card to work with the bus and associated peripherals. I've never had any experience with Zilog processors so I thought it might be fun to give that a go as well (and add to the 8-bit CPU bus collection). I came across the RC2014 and RomWBW websites and they quite appealed to me so I designed a Z80 board that incorporated features to make it compatible - in particular, the memory and ROM paging.

Digicool already had a Motorola I/O Card (with a 68B50) similar to that used by RC2014 albeit in a different I/O port and also 9918/9938/9958 card (amongst other I/O cards). So I set upon adding a new platform configuration for MECB in my local version of RomWBW. In the process, I also made up a parallel IDE interface (similar to the RC2014 version and also supported by RomWBW) and a combined "front panel" board with RTC. So far, all of these work really nicely with RomWBW (although I still have some debugging to do with the RTC). Kudos to Wayne Warthen (and contributors) for an amazing job in making RomWBW highly flexible and configurable and also to the RC2014 community for making schematics available!! Here is a happy snap of the system in the process of booting up and humming away at 10 MHz:

I have also tested it with the 9958 board and that also seems to work (well, I get a cursor and I can call the bios routines to write text to the display). My next plan, after getting the RTC working, is to add a keyboard and allow the system to work in a self-contained way.

I've made the schematics and board layouts available here:
MECB Z80

Cheers,

Emil.

[wwarthen]

Hi @epaell,

This is awesome. I am always pleased to see RomWBW living on a new hardware platform. That is kind of its mission in life. 😀

I would be happy to make it an official platform supported by RomWBW if you want. I would just need to work with you to incorporate your changes into the official repository here.

Thanks, Wayne

[epaell]

That would be fantastic as I've been wondering how to make this more accessible (I'm not a particularly proficient GitHub user and struggle with anything but the basics). The modifications so far have been really minimal and I hope I have made the changes in a manner that is consistent with the overall structure of RomWBW:

I modified four of the existing files in Source/HBIOS:

hbios.inc

• Added after line 214
  PLT_MECB .EQU 28 ; Digicool Things MECB KITS

plt_pretty.inc

• Added after line 202

#IF (PLATFORM == PLT_MECB)
	.DB	"      _/_/      _/_/  _/_/_/_/_/_/    _/_/_/_/_/    _/_/_/_/_/_/",10,13
	.DB	"     _/_/_/  _/_/_/  _/_/          _/_/      _/_/  _/_/      _/_/",10,13
	.DB	"    _/_/  _/  _/_/  _/_/          _/_/            _/_/      _/_/",10,13
	.DB	"   _/_/  _/  _/_/  _/_/_/_/      _/_/            _/_/_/_/_/_/",10,13
	.DB	"  _/_/  _/  _/_/  _/_/          _/_/            _/_/      _/_/",10,13
	.DB	" _/_/  _/  _/_/  _/_/          _/_/      _/_/  _/_/      _/_/",10,13
	.DB	"_/_/  _/  _/_/  _/_/_/_/_/_/    _/_/_/_/_/    _/_/_/_/_/_/_/",10,13
#ENDIF

std.asm

• Added
  TMSMODE_MECB .EQU 12 ; MECB V9958

tms.asm

• Added after line 174

#IF (TMSMODE == TMSMODE_MECB)
TMS_DATREG	.EQU	$80		; READ/WRITE DATA
TMS_CMDREG	.EQU	$81		; READ STATUS / WRITE REG SEL
;TMS_PPIA	   .EQU	$84		; PPI PORT A (Note keyboard not yet implemented)
;TMS_PPIB	   .EQU	$85		; PPI PORT B
;TMS_PPIC	   .EQU	$86		; PPI PORT C
;TMS_PPIX	   .EQU	$87		; PPI CONTROL PORT
;TMSKBD      .EQU  TMSKBD_PPK
TMSKBD      .EQU  TMSKBD_NONE
		DEVECHO	"MECB"
#ENDIF

• Added after line 374

#IF (TMSMODE == TMSMODE_MECB)
	PRTS("MECB$")
#ENDIF

And I added the following two files:

cfg_MECB.asm
cfg_MECB.txt

Config/MECB_std.asm
MECB_std.txt

I'm not sure if it is a user error kind of thing but for some reason I can't upload .asm files but it works fine if I rename to .txt.

Cheers,

Emil.

[epaell]

Apologies, I've made a minor change to the front panel port and shifted it from $C4 to $C1 (there was no reason to leave the $C1-$C3 gap given that the front panel IO and RTC are on the same board for the MECB (thus leaving more space for devices that might need more ports).
cfg_MECB.txt

[wwarthen]

OK, I will add this to the repository. However, I am in the final stage of releasing a new stable version v3.6. I don't want to introduce this prior to publishing the new stable version. I will add the MECB platform shortly after releasing v3.6.

Thanks, Wayne

[epaell]

No problems - that's absolutely fine.

[wwarthen]

With commit 123264f, I have integrated the MECB files and completed the new platform setup in the build process. The latest prerelease includes the MECB binaries. I don't have the hardware to test the build. If there are any issues, please post in Issue #671.

Thanks, Wayne