Interesting. RS232 has always been marginal on the Model 100 but it's news to me that there was a needed repair.
I'm also interested to understand more about what's going on with the backpack. You said it had to do with handshaking signalling and loopback, and what sounds like a powersave mode in the backpack reacting to the low signal. What is "loop" feature on Backpack? Why is it necessary? Does Backpack not connect or assert DSR? -- John. On Fri, Jan 13, 2023 at 1:44 PM <[email protected]> wrote: > Some of the original M100s have the wrong resistors in part of the RS232 > handshake circuit. The voltage drop is so high that with the signal looped > back it is just barely sufficient. The Backpack eavesdrops to know when to > power itself back up and this minuscule additional load is too much. The > symptom is that the Backpack responds once and then stops. > > I have tried to attach a tech bulletin that Tandy put out back in the day > that describes the fix. The alternative is to set both lookback switches > away from the dot. The Backpack does not eavesdrop in this configuration so > it can't wake itself up. You can adjust the timeout to compensate. > > This is only the third M100 I've com across with this issue. I have one of > them too 😊 At some point in the future I'll do a video on the fix per the > Tandy tech bulletin. > > Jeff Birt > > -----Original Message----- > From: M100 <[email protected]> On Behalf Of Philippe Van > Lieu > Sent: Friday, January 13, 2023 2:02 PM > To: [email protected] > Subject: [M100] Backpack-Plus with REXCPM help > > Hello everyone! I recently bought the Backpack-Plus for the M100, and I > LOVE the thing. I want to thank you Jeff Birt/soigeneris for making this > wonderful device to help keep these classic machines alive! > > That said, I'm having an issue getting it to work properly on my > REXCPM-powered M100. Fortunately the Backpack works fine on my normal > M100 so I figure the Backpack isn't the issue, but every time I try to run > it on TS-DOS on my REXCPM'd M100, I get a "device not ready" error albeit > after working only once beforehand. > > I read the instructions and tried to adjust the timeout/sleep settings to > something like 5 minutes via the CLI, but that didn't affect it. I also > read the "Use with CP/M-100 and REXCPM", but that's just the initial > installation instructions. I also saw the suggestion of using TS-DOS v4 or > higher, but that also didn't have a positive effect. > Finally, a saw the paragraph on page 45 about making sure that the LOOP > switch is set to LOOP in order to ensure TS-DOS keeps the Backpack-Plus > awake, but neither that nor power cycling the Backpack-Plus woke it up. > > So I'm at a loss on what I can do to get it working. I went through the > M100 mailing list archive, and it sounds like other REXCPM users haven't > had any issues using the Backpack... so I suspect that maybe I'm doing > something wrong. I'm open to any suggestions, and I thank you ahead of time > for your help! > > --- Philippe > >
