Atom Z80 board....

discussion of games, software, hardware & emulators relating to the Acorn Atom
Prime
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Atom Z80 board....

Postby Prime » Sat Feb 28, 2015 8:38 pm

Hi all,

Is there a memory map or complete schematic available for the Atom Z80 card?

I've seen the ones available at : http://www.acornatom.nl/hardware/cpm/cpm-sch.html

But they don't seem to be completely accurate / complete as there are signals that appear not to be generated anywhere (/mrco for example).

Does the Z80 board need a second 6522 at the atom end, or could the system 6522 be used ? If it needs a second 6522, I may add one to the re-engineered 80 col board.

Cheers.

Phill.

eric
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Joined: Mon Apr 21, 2014 1:12 pm

Re: Atom Z80 board....

Postby eric » Sat Feb 28, 2015 9:17 pm

Hi Phil,

I have one of these cards still running in my old lady .. fully operational .. running CP/M ... and also giving ADOS and GDOS functionality within the atom .. depending on the mode how you booted ...

Indeed at has an extra via in the memory map to connect .. I think it will not be a big issue if you want to use the existing VIA in stead of an extra one because i still have the sources for the terminal program running on the atom where it is possible to change the port addresses and recompile (i think it compiles fine in salfaa 2.6) ..

Let me know if you are interested in anything and i will send it to you ..

Grx..

Eric

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roland
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Re: Atom Z80 board....

Postby roland » Sat Feb 28, 2015 9:52 pm

Prime wrote:Is there a memory map or complete schematic available for the Atom Z80 card?


I have searched for the original documentation but the schemas on the acornatom.nl site are a good copy of them. I will make a scan next week and post them for you. The memory map is simple. At boot time, the eprom is selected but it will be switched of after initialization so the Z80 has 64kB ram available. I have to search where I read this...

Prime wrote:Does the Z80 board need a second 6522 at the atom end, or could the system 6522 be used ? If it needs a second 6522, I may add one to the re-engineered 80 col board.


Most people who build the Z80 board used an additional 6522 so that the system via was still available for printing. I never build or used one but I can't imagine why it wouldn't work with only the system via.
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Prime
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Re: Atom Z80 board....

Postby Prime » Tue Mar 03, 2015 9:40 am

Aha.... pointing google translate at :

http://www.acornatom.nl/atom_handleidin ... pm_hl.html

Has yeilded most of the info I need :)

Cheers.

Phill.

Prime
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Re: Atom Z80 board....

Postby Prime » Fri Mar 06, 2015 2:14 pm

Ok one thing I can't figure out is where does the IRQ line from the FDC go (labeled /FDCINT on the schematic).

It's connected at the FDC end but doesn't seem to be connected elsewhere ?

Cheers.

Phill.

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roland
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Re: Atom Z80 board....

Postby roland » Fri Mar 06, 2015 4:03 pm

I took my unbuild Z80 board and I checked the trace from FDCINT (pin 37). It goes to D5 pin 29 (PB2). This is different than in the diagram. In the diagram pin 29 is connected to pin 39 of the FDC and pin 14 of D8.

On the board is pin 39 of the FDC via a resistor connected to +5V.

I will dig out the original diagram and compare this to the published diagram.
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roland
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Re: Atom Z80 board....

Postby roland » Fri Mar 06, 2015 6:27 pm

I have made some hi-res scans from the original diagram and the pcb. Maybe that helps to figure out the IRQ line. It looks like the two diagrams are a little bit different.

You can download them at http://diy.acornatom.nl/download/z80-tiff.zip (30MB)
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bprosman
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Re: Atom Z80 board....

Postby bprosman » Sat Jun 25, 2016 2:59 pm

Just kicking an old topic, looking at this (as I am planning a Z80 copro).

As well as for the WD1793 as for its replacement the MB8877 pin 37 is not the interrupt pin. Pin 37 is switching "Double Density".
/DDEN indeed goes to PB2
Didn't check it but think /IRQ will go to PB7 and is pulled up.

Looks like in the diagram scanned by Roland pin numbers 37 and 39 are switched. Just the numbers not the functions.

Kind regards, Bram

bprosman
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Re: Atom Z80 board....

Postby bprosman » Tue Jul 25, 2017 11:16 am

Kicking an old topic, its my holiday so time for the CP/M board again. Looking at the original (Dutch CP/M) board I see that they used a 16MHz clock divided by 4 for the system clock, was this done for an easy interface to the Dynamic RAM ?

Kind regards, Bram

silvercreekvalley
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Re: Atom Z80 board....

Postby silvercreekvalley » Tue Aug 01, 2017 11:13 am

Hi

I have one of these boards fitted to an expanded Atom. If there is any info you need let me know. I have a fair bit of documentation which I've been meaning to scan too.

bprosman
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Re: Atom Z80 board....

Postby bprosman » Wed Aug 02, 2017 11:25 am

Thanks for the reply (and offer), I do have the full set of doc (thanks to Roland, a little bit above here in the treat) as well as a HiRes scan of the PCB. As I intend to build a CP/M extension built with static RAM and was curious about why the choice of a 16MHz oscillator divided by 4 and not a 4MHz crystal.

Best regards, Bram


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