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RE: [N8VEM-S100:3228] Minimal Z80 system startup questions.

I agree 100% Gary. 

One of the great advantages of the S100 bus is that you can add (or remove) components in stages to get things working.

As Gary stated, start with a Z80 CPU board preferably one with its own onboard ROM. 

Show you can on reset get it to HALT. 76H in ROM, first at 0h, later at the “boot” address.  No RAM is required.

Add whatever board you are using for character displays (e.g. our Console-IO board).

In ROM continuously output a character to the screen. Again no RAM is required

Add whatever console input board you are using.

Continuously output the last keyboard character entered. No RAM is required.

Next add RAM board.

Either use my “stackless” monitor Gary mentioned below or write a routine to place 76H in RAM and jump to there. Then a routine to display the keyboard character…

Next add the Z80 Master monitor (or your own) and thoroughly check hardware.  Copy, move memory etc.


To bring up CPM, by far, the easiest is a non-banked version of CPM3 on the Dual IDE board.  The web page shows how to do it.


I know this is a long process but believe me it’s the fastest in the end.  Plopping in 4 or 5 new boards and hoping to get everything working at once is difficult.  Not impossible BTW, if you know your electronics and use a logic probe an experienced hardware guy can quickly nail a problem. The reason I have so much “bling” LED’s is they quickly focus in on where problems are.


Good luck



From: yoda [mailto:yo...@r2d2.org]
Sent: Friday, April 25, 2014 7:18 AM
To: n8vem...@googlegroups.com
Cc: mon...@vitasoft.org
Subject: Re: [N8VEM-S100:3228] Minimal Z80 system startup questions.


trying the big bang approach never has much success - good luck.  You need to do this piece meal.  I actually have done this as I had no S100 system prior to building the boards.  My approach was to first write a simple loop in ROM that did an out to the serial port in a loop.  I plugged in the CPU board populated and the minimal parts on serial board and made sure the CS was pulsing on the SIO chip.  Next I proceeded to write a hand initialization of the SIO chip and a simple loop to output a character in a loop - I call that my scream test.  Once I have that working I know the CPU and SIO board are working.   Next I took John's RAM test that is unrolled and does not use a stack to bring up the memory board.  Again simple loops on memory addresses are useful for making sure basic address decoding in working on the memory board.  Once memory is working get the Monitor loaded in ROM.  I don't have the floppy board but John has pretty good bring up notes on his page.  Bringing up any board is a similar process - populate the bus and control logic and use simple loops to make sure address decode and CS functions work - them populate more of the board and write small exercisers to test new function added.  This may seem to take longer but in the long run it is shorter and less chance of damaging chips.  Also it is a lot of fun debugging and building this way.

On Friday, April 25, 2014 8:47:49 AM UTC-5, gek...@gmail.com wrote:

John -

Will do - I was hoping to find someone using the serial board as a console and a working bios.  Without a currently working S100 system I was trying to cut-out one variable in bringing up 4 boards at once.

I do have a S100 system that I haven't booted in several years.  I may tackle that first so I have a working test setup.

- Gary

On Thursday, April 24, 2014 5:23:37 PM UTC-4, monahanz wrote:

All of  the software is on the S100Computers web site Gary.  Go to the software section.  I don’t have a  CPM 2.2 version (only 3.0).  While I could copy a disk for you the console IO ports would not match up unless you are using the Console-IO board.    You really have to modify the code for own BIOS.   Easy to do.





From: n8ve...@googlegroups.com [mailto:n8ve...@googlegroups.com] On Behalf Of gek...@gmail.com
Sent: Thursday, April 24, 2014 12:53 PM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:3228] Minimal Z80 system startup questions.


I'll hopefully soon have a Z80 CPU card, a ZFDC floppy controller, 4mb SRAM and Serial IO cards.

I'm hoping to simplify bringing them all on line, and avoiding re-inventing the wheel.

I'd be interested in hearing from anyone who has a working system and might be able to provide known working monitor code, a bootable CP/M 2.2 or 3.0 disk or images and suggested jumper/switch settings. 

Many thanks in advance!

- Gary

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