41CL UPDATING PROBLEMS

[Monte Dalrymple]

It sounds like something is wrong with the physical connection between the CL and
the computer. Something similar happened to me once, and I resolved it by
unplugging the serial cable from the CL and plugging it back in. I routinely give the
plug a little twist to wipe the contact area of the plug/jack combination. Make sure
that the plug is fully seated in the jack.

The MMU is disabled whenever the power-on-reset circuit on the CL board is
tripped. The plug/jack used for the serial port is not ideal, and during insertion or
removal it can cause a power supply glitch, which will trip the POR. This disables
the MMU but does not affect the MMU programming in RAM. So, like Sylvain, I
always execute an MMUEN after inserting or removing the serial plug.

The RS232 driver on the CL board will not power up unless it detects a valid level
on the receive data line. This is why CL-CL transfers require special handling, but
if the serial driver on the computer is set up the same way both ends will also just
sit there waiting for a valid level. You can force the CL serial port to turn on by
executing the SERON function that is available in YFNX.

The timeout delay for the CL is about 30 seconds. It sends the CMOPEN byte
and then waits this long before signalling TIMEOUT. If this message appears
much faster than that something funny is going on, but I don't know what.

I have had a serial cable fail before, although it was obvious when it did,
because the the plug broke during insertion. Yes, it tripped the POR and was
a pain to get the broken piece out of the calculator. But this was the cable
that I have been using since the very beginning and the plug is out on my desk
getting banged around all the time.

Have you ever done a serial transfer to/from the CL before? That is one thing
that I am not able to test before I ship, so there is a very remote possibility
of it not working.

But my money is on a bad connection between the plug and the jack on the CL.