Dumping the ROM from a XEGS?

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adrm
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Dumping the ROM from a XEGS?

Postby adrm » Mon Oct 15, 2018 10:21 pm

I have a non-working Atari XEGS that I'm trying to fix. I have already replaced two RAM ICs, as they were clearly faulty.
But the machine will still not show anything but a black screen, and no sound appears if I try to run the built in Sound test.

No chips are hot now that the RAM has been replaced, and the scope doesn't show me any obvious culprits ... yet.

I have un-soldered the ROM, and I'm attempting to read it using a TL866-II Plus EPROM reader/writer.

Problems:
1)
I always get a "pin detection type error" pointing to pin 1.
This might not necessarily point to a problem in itself and disabling "pin detection" in the software bypasses this.
2)
Whatever 27C256 type EPROM device (which is interchangeable with the XEGS ROM) I have selected in the reader software, it will only read 100% "00 bytes" or only "08 bytes".
I.e. either the ROM is faulty or the TL866 is not reading it correctly.

Question:
Has anyone managed to read these ROMs using the TL866-II ?
(I can read other devices on the TL866, e.g. 27128 EPROMS)

ijor
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Re: Dumping the ROM from a XEGS?

Postby ijor » Tue Oct 16, 2018 12:26 pm

Note that Atariage is a forum more specialized in the 8-bit. You will probably get more help there. Having said that ...

This is not an EPROM. It is a masked ROM with a different pinout. Most EPROM burners can't read masked ROMs. You might need to build a special adapter.

adrm
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Re: Dumping the ROM from a XEGS?

Postby adrm » Tue Oct 16, 2018 5:17 pm

Thank you, ijor.
I'll try Atariage.

I have read, several different places, that the 27C256 is functionally & pin compatible with the Atari ROM, and are used to replace defect ROMS.
That made me assume my TL866 would be able to read it as if it were an EPROM.

adrm
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Re: Dumping the ROM from a XEGS?

Postby adrm » Tue Oct 16, 2018 7:51 pm

Quick update.

Problem solved by flashing an EPROM (27C128) with only the OS part of the XEGS' ROM, i.e. without BASIC and Missile Command.


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