Acorn ROM/RAM Podule Manager

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SteveBagley
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Acorn ROM/RAM Podule Manager

Post by SteveBagley » Thu Jan 09, 2020 8:42 pm

Does anyone know if there is a dump of the Manager ROM found on Acorn's (or Computer Concepts) ROM/RAM podule available online or is anyone able to make one?

Steve

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IanS
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Re: Acorn ROM/RAM Podule Manager

Post by IanS » Thu Jan 09, 2020 9:22 pm

SteveBagley wrote:
Thu Jan 09, 2020 8:42 pm
Does anyone know if there is a dump of the Manager ROM found on Acorn's (or Computer Concepts) ROM/RAM podule available online or is anyone able to make one?
This ok?
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rom_podule_0.07.zip
(4.7 KiB) Downloaded 12 times

SteveBagley
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Re: Acorn ROM/RAM Podule Manager

Post by SteveBagley » Thu Jan 09, 2020 10:33 pm

Yep, looks great thanks.

Steve

alexgibson
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Re: Acorn ROM/RAM Podule Manager

Post by alexgibson » Fri Jan 10, 2020 9:43 pm

Is it this that you are referring to Steve?
http://chrisacorns.computinghistory.org ... RAM_UG.pdf

Cheers
Alex

SteveBagley
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Re: Acorn ROM/RAM Podule Manager

Post by SteveBagley » Fri Jan 10, 2020 10:27 pm

Yea -- I'm attempting to write an extension for Arculator to emulate it (mainly to get used to the API before implementing some more interesting podules.

Just trying to reverse engineer how the podule maps the ROM's into the podule address space at the moment, other than that it looks reasonably straight-forward.

Steve

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IanS
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Re: Acorn ROM/RAM Podule Manager

Post by IanS » Fri Jan 10, 2020 10:38 pm

SteveBagley wrote:
Fri Jan 10, 2020 10:27 pm
Just trying to reverse engineer how the podule maps the ROM's into the podule address space at the moment, other than that it looks reasonably straight-forward.
Have you seen the circuit diagram on the last page of the Acorn manual? (my ROM image was from the Acorn version).
http://chrisacorns.computinghistory.org ... _Guide.pdf
It doesn't give detail of the GAL, but it should give you some clues.

SteveBagley
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Re: Acorn ROM/RAM Podule Manager

Post by SteveBagley » Fri Jan 10, 2020 11:05 pm

IanS wrote:
Fri Jan 10, 2020 10:38 pm
Have you seen the circuit diagram on the last page of the Acorn manual? (my ROM image was from the Acorn version).
http://chrisacorns.computinghistory.org ... _Guide.pdf
It doesn't give detail of the GAL, but it should give you some clues.
Yep, definitely useful -- and I have the podule loader open in Ghidra as well ;) Things are working rather well so far, I've happily got it loading the podule to the point I can mount ROMFS and load ROMIT into BASIC :)
Screenshot 2020-01-10 at 22.53.54.png
Screenshot 2020-01-10 at 22.54.20.png
From what I can tell so far, it seems the ROM podule reads the ROMs via a 2K window mapped from 0x0000 -> 0x1FFF in the podule space. The window can be moved to different addresses and ROMs by writing to address 0x2000 (which I guess corresponds to the 74HCT273 at IC13). The bottom six-bits of this register store the upper six-bits of the address (BA11-BA16), while the remaining two bits (bits 6 and 7) are used to select the ROM (S0, S1 on the circuit diagram) in combination with a third bit.

The ROM is selected by the three bits S0-S2 which feed a 74CHT138 used to generate /CE to the relevant ROM. S0-S1 come from the register at 0x2000, but S2 is set by writing to either 0x3000, or 0x3800 depending on whether it is to be set to 0 or 1 respectively. I think S2 is stored within the PAL.

Investigations continue since I think there's more to the PAL though, since D0 also seems to be connected into the PAL (and LA10 -- but I suspect that might be used to buffer it), and there's also the SDE signal which feeds the 74HCT138.

Steve

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Re: Acorn ROM/RAM Podule Manager

Post by SteveBagley » Sat Jan 11, 2020 12:05 am

Have just tested it with the BBC View ROM 'inserted' as well as the manager ROM, and I'm able to access that and run it in the 6502 Emulator :)

Steve

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IanS
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Re: Acorn ROM/RAM Podule Manager

Post by IanS » Sat Jan 11, 2020 11:35 am

SteveBagley wrote:
Fri Jan 10, 2020 11:05 pm
Investigations continue since I think there's more to the PAL though, since D0 also seems to be connected into the PAL (and LA10 -- but I suspect that might be used to buffer it), and there's also the SDE signal which feeds the 74HCT138.
I could probably do some monitoring with a logic analyzer if you need any clarification on what is happenening.

Could it be latching the state of DO when writing to to the podule for one or more of the output signals?

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Pernod
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Re: Acorn ROM/RAM Podule Manager

Post by Pernod » Sat Jan 11, 2020 12:00 pm

Were there many Archimedes specific ROMs intended for use with this podule? There's obviously the Computer Concepts Inter series, which I presume differ from the BBC versions as they wouldn't require the PAL carrier boards, are these dumped? Any others?
- Nigel

BBC Model B: ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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jgharston
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Re: Acorn ROM/RAM Podule Manager

Post by jgharston » Sat Jan 11, 2020 1:26 pm

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.32
(C) Copyright J.G.Harston 1989,2005-2020
>_

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