HP9835 ROM questions

[dfnr2]

(07-10-2016 05:03 PM)Paul Berger (Canada) Wrote:  I can provide you with a pinout of the ROM slots but be aware that the logic level on those card slots is 6V which makes it somewhat inconvenient to use them with modern devices.

I would be interested in the pinout. Do you know what architecture the ROM modules use? As I understand, any module can go in any slot, without any conflict. Do they use relocatable code with each slot mapped to a fixed address, or is there decoding built into the modules, with each module at a fixed address independent of the slot? In a ROM replacement board, would the order of images in the EPROM make a difference?

Quote:What I did was create a card that plugs into one of the connectors for RAM cards which are the more usual 5V logic level. My design was posted on hpmuseum.net, http://www.hpmuseum.net/upload_htmlFile/...AMCard.zip unfortunately on the page it only mentions RAM card but the packages contains the documentation for my ROM card as well as a schematic for the 9835 64K RAM card. I have also built a RAM expansion card using more modern static RAMs so now my 9835A has a little over 512K of RAM. I have not put together any formal documentation for my RAM card yet. Both of these cards where constructed as hand wired prototype cards. If you have questions send me an email and I will assist.

Definitely interested in both RAM and ROM options. Do you by any chance have timing diagrams for the bus? I looked at the RAM and ROM schematics. Is there a reason the RAM schematics seem much more complicated, or is it just that you reduced chip count by using PLD's in the ROM card?

Quote:I have no experience with the test ROM in fact this is the first time I have heard of anyone having one. If you have not already done so you should get the service manual from hpmuseum.net as it explains how to use the service ROM. I would be very interested in a dump of this ROM and can help you with dumping it.

I would love to dump it and will take any help I can get. The only thing is that when I plug it in, the machine looks dead on poweron. Perhaps an adapter can be built to probe the ROM with a microcontroller, without plugging in to the machine?

Thanks,

Dave