For Sale: HP-71B MultiMod ROM Emulator

[mfleming]

One low probability event (LPE?) that occasionally occurs when the MM is hot plugged or powers up after batteries are inserted is that the boot loader thinks it sees a Break condition (Rx input held low) and waits for a client connection instead of transferring control to the emulator. I have the input configured with an internal weak pullup, but with nothing connected to that input pin it might just look low to the boot loader immediately after a reset.

If the MM doesn't respond after the Poke command/power cycle, try resetting the MM by pulling the J2 power jumper, or by briefly shorting the Gnd and MCLR pins on the serial port. I'm going to summarize this and a few other things on a page of the Programming Pad document so it can serve as a quick reference guide/FAQ. As mentioned earlier, user manuals written by engineers tend to be waaay too long...