Need advice on dumping 80C51 ROM

[Mike]

I have an 80C51 equivalent IC chip, P80C521, and i think it has internal
either 8 or 16K of ROM. no external ROM on the board.

Im familiar with Atmels and programming of atmels, but can someone point me
in the right direction for a simple programmer/reader for this P80C521 chip?
the chip is a display controller, no datasheet available for the display, so
I need to dump the ROM so I can run it in a disassembler.

any ideas? thanks.

 

[Roger Hamlett]

I have an 80C51 equivalent IC chip, P80C521, and i think it has internal
either 8 or 16K of ROM. no external ROM on the board.

Im familiar with Atmels and programming of atmels, but can someone point
me in the right direction for a simple programmer/reader for this
P80C521 chip? the chip is a display controller, no datasheet available
for the display, so I need to dump the ROM so I can run it in a
disassembler.

any ideas? thanks.

If I remember correctly, the 521, has custom ROM programmed at the
factory. It is not externally accessable. The 541, has ROM that can be
programmed. The chip manufacturer (AMD?), will probably still have the
original ROM data, but will also probably still be bound by their original
agreement not to disclose this. Your only 'shot', will be to find who the
chip was programmed for, and see if they can help you.

Best Wishes

 

[Franc Zabkar]

There is a datasheet at
http://www.datasheets.org.uk/datasheet.php?article=2648543

If I remember correctly, the 521, has custom ROM programmed at the
factory. It is not externally accessable. The 541, has ROM that can be
programmed. The chip manufacturer (AMD?), will probably still have the
original ROM data, but will also probably still be bound by their original
agreement not to disclose this. Your only 'shot', will be to find who the
chip was programmed for, and see if they can help you.

Best Wishes

FWIW, the P87C521 might be an EPROM version of this chip. IME the
existence of an EPROM version usually implies that the ROM version can
be externally accessed.

- Franc Zabkar

 

[Mike]

it doesnt have a window, so its ROM. man i wish i could dump this ROM and
disassemble it to see how it works.

 

[Roger Hamlett]

it doesnt have a window, so its ROM. man i wish i could dump this ROM
and disassemble it to see how it works.

The point being made, was that _sometimes_, if there is an equivalent
EEPROM version, the circuitry to allow the ROM contents to be accessible
to a device programmer is left in the die. If so, it might be worth
tracking down the programming algorithm for the 87C521, and trying the
'read' part of it. Some commercial programmers will also still contain
support for this device. For example, the 'ROMMAX' from Action Electronics
lists this.

Best Wishes

 

[martin.shoebridge]

Sometimes you can build an external rom "extractor". This code executes and
reads internal code via MOVX instruction. However, I would expect that the
internal rom has been code protected by fuses so I think this highly
unlikely. It could be that ROM based cores are internally protected by
default!!!
In the old days, I was able to read 'protected' devices by gradually
lowering the target vcc and trying to read the device with a conventional
programmer.Specifically, this was a Philips device.....

 

[Mike]

ugh. sounds like a nightmare. I think i will just re-write the firmware for
an ATmega and useing an ATmega and just trash that 8051.