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Hi,

I have a problem with my PM6/7 daughter board from Doc.

It works fine without access to external ROM, but as I put the jumper and boot, the CEL is solid.
I have checked all my PCB for continuity 3 times, and everything is OK.

BUT there is a strange thing : If I remove my AT29C256 after boot ECU with jumper, and plug it on my ROM programmer for read, some groups of bytes are corrupted ! randomly ! On time at the beginning, on time in the middle !

I re-test with the pin #1 of 29C256 (Write Enable) don't plug on daughter board socket (in the air), and SAME thing ! 839 bytes corrupted !

I have watched pin #28 of CPU (connected to #1 of 29C256) with oscilloscope and there is a square signal 5V with 60ms period. Is not strange to have A15 of CPU bus connected to /WE of flash ROM ??? (16 wire to access 32k ?)


Is anybody can help me ? Idea ?

Thank you !

I have strapped 5V on /WE of 29C256, bytes don't go anymore

But always a solid CEL ...

AT29C256 really works on Doc daughter board !???

It seems that square signal on #28 CPU (A15) destroy the flash rom content !

Is A15 really needs with only 32kb to access ???

No, A15 isn't needed for 32k access.

Cut the track from CPU pin 28 to Eprom Socket Pin 1.
Connect only the Eprom Socket Pin 1 to VCC (Eprom Socket Pin 28).

Tested and working.

Doc

Thank you Doc !

I will try this, but when I strapped 5V on FlashRom pin #1 (yesterday), I had a solid CEL to. ;(

More informations later !

It's OK, it works fine with a *good* BIN !