HP-71B MultiMod ROM Emulator - Issues ?

[mfleming]

(03-27-2021 03:35 AM)Sylvain Cote Wrote:  Hello Mark,

First impression, pcb is clean, solder joins are impeccable, superb quality, nicely done, congratulations.
Daniel has also done a great job on the MultiMod casing, it's way better than the ones from CMT and HHP.

Thanks Sylvain! Only headers are hand soldered, components are reflow soldered. Dan is indeed to be congratulated on the enclosure design. Pictures don't do justice.

Quote:All three modules works.
I was confused at first because PEEK$("2C000",1) always report "0" even after doing a POKE "2C000","1".
I am using VER$ to validate that the module is active, PEEK$ would have been better thought.

Only the ROM data are mapped into the Read address space. Never occurred to me to map the CR I/O address range into the Read rather than just the Write. There are obvious possibilities for status presentation though. Could be done, I'll look into it.

Quote:It seems that there is a compatibility issue with some 71B.
All three modules work on S/N: 2713A00041 but none works on S/N: 2410A00146.
I know the card reader port works on S/N: 2410A00146 because it usually hosts a working FRAM71 module.

Thankfully I was dumb-lucky enough to to acquire a second 71B during development, an early 2406A metal back model (original model I was using was 2724A). These very early models have a significantly different bus access timing profile compared to the published HW IDS specs. My early 71B failed or locked up when first used, so I had to adjust emulator timing to match. J-F has some 'scope traces illustrating the differences in timing vs. later models. Timing compensation could likely be possible for these early, I believe slower clock models, but it would need to be a separate code branch. A fix for this would present a timing headroom risk for the bulk of the later models, so would need to be managed and distributed separately. A change wouldn't be hard but you'd have to be the test guinea pig on this one Best to see if any others are affected first.

Quote:I will be testing the MultiMod modules on more machines tomorrow.

Thank you very much for doing so!

Quote:I am still using the default configuration on all three MultiMod modules.

Here's a bit of fun. Try poking a "1" to the 2C000 address so that uLib52 isn't enumerated, then execute a uLib command. It works, at least for me, despite the fact the uLib ROM doesn't show in VER$, SHOW PORT, or CAT :PORT(5.03). Ack! Code hairball.

~Mark