HP85 Programmable ROM cardtridge 82929A-service ROM not working-


I have inserted a copy of the Service ROM (Rev.B) in a 82929A programmbale ROM module, in order to perform some tests.

According to the instructions manual, after 15 seconds a message would display "Service ROM: Select Test A-V". However, I cannot see any message at all. The machine starts as usual, without any message on the display.

I have placed the ROM on a 2764 EPROM on socket S8, and have set the DIPs S1 to set the address of the ROM. My setting is 01000000 (HSB first; that is just pin 7 ON).

Is it necessary to place the Service ROM at at a precise address? By the way, does the 82929A need to be placed in a certain slot ?


Ok quick course on how the series 80 machine address add on ROMs. The address in the memory map where the ROMs appear is fixed, and all of the installed ROMs are bank selected in and out of that address. The selection is based on the ROM number assigned to it for example your service ROM is 224 decimal or 0xE0. For that to work on the 82929A the switches corresponding to the socket the ROM is in would need to be set to 0xE0 or 11100000 binary.

The 82929A can go into any slot.


Thanks, now it works!

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