41CL MMU Reset upon serial cable insert/remove

[rprosperi]

Another thread documented my issues troubleshooting getting my 41CL to do serial transfers. Thanks to lots of help and a specific tip from Michael Fehlhammer, I've been able to get this working.

Now, every time I insert or remove the serial cable on the 41CL end (plugged-in already on the PC side) the MMU is disabled. Note the configuration is preserved so I need only re-enable the MMU to continue.

A careful re-reading of the manual indeed says clearly that the 2.5mm plug should be inserted into the 41CL prior to connecting the DB9 end to the PC. I will test this tonite to see if it works w/o MMU reset, but I'm confidant it will work OK.

Have other 41CL users had this same experience?

[Ángel Martin]

(02-26-2015 02:04 PM)rprosperi Wrote:  Now, every time I insert or remove the serial cable on the 41CL end (plugged-in already on the PC side) the MMU is disabled. Note the configuration is preserved so I need only re-enable the MMU to continue.

Have other 41CL users had this same experience?

It may be because you're plugging the cable to the CL with the other end already connected to the PC COM port?

If you first plug the CL end and then the PC end this should not occur.

[ElectroDuende]

(02-26-2015 02:04 PM)rprosperi Wrote:  A careful re-reading of the manual indeed says clearly that the 2.5mm plug should be inserted into the 41CL prior to connecting the DB9 end to the PC. I will test this tonite to see if it works w/o MMU reset, but I'm confidant it will work OK.

I don't have a CL, but I suspect where the problem can come from. In a jack type connector, the pins are mis-connected while the jack is inserted (the tip will touch the base and sleeve contacts while traveling inside), so unexpected signals can arrive to the calculator. On the other side, in a DB9 connector a pin will never contact any other one during the connection process.

[rprosperi]

(02-26-2015 02:44 PM)Ángel Martin Wrote:  It may be because you're plugging the cable to the CL with the other end already connected to the PC COM port?

If you first plug the CL end and then the PC end this should not occur.

As I expect and will verify tonite, thanks.

(02-26-2015 03:08 PM)ElectroDuende Wrote:  I don't have a CL, but I suspect where the problem can come from. In a jack type connector, the pins are mis-connected while the jack is inserted (the tip will touch the base and sleeve contacts while traveling inside), so unexpected signals can arrive to the calculator. On the other side, in a DB9 connector a pin will never contact any other one during the connection process.

This makes perfect sense looking at the 'pin-out'. Looks like the tip (PC Rx) touches ground while being "pushed-in" and seems to cause a minor power reset.

Its a pain of course to have to replug the DB9 upon each use, but I primarily wanted to confirm that other users are having the same experience and results.

Thank you.

[Monte Dalrymple]

(02-26-2015 03:08 PM)ElectroDuende Wrote:  I don't have a CL, but I suspect where the problem can come from. In a jack type connector, the pins are mis-connected while the jack is inserted (the tip will touch the base and sleeve contacts while traveling inside), so unexpected signals can arrive to the calculator. On the other side, in a DB9 connector a pin will never contact any other one during the connection process.

Yes, I am sure that this is where the issue comes from. The jack/plug combination was chosen solely because it was possible to mount the jack in a blank Port cover. I know it's a kludge, but I wanted to use blank Port covers to hold the connection. I couldn't find a better way to do it inexpensively.

[rprosperi]

(02-26-2015 06:20 PM)Monte Dalrymple Wrote:  Yes, I am sure that this is where the issue comes from. The jack/plug combination was chosen solely because it was possible to mount the jack in a blank Port cover. I know it's a kludge, but I wanted to use blank Port covers to hold the connection. I couldn't find a better way to do it inexpensively.

Indeed this is the issue as there is no problem with MMU reset inserting and removing the cable when the DB9 is not plugged into the PC.

I don' think this really is a kludge since this is the only (reasonably cheap) type of std serial connector that can fit into a port cover. Also, the procedure is clearly noted in the manual.

Mostly its a case a being an overly nervous new mother. But the baby is healthy!

Thanks to all for comments and advice.