This note is regarding the Jumper pins on the Communications board
"PC 7600" PCB of Controller-A. Which was never confirmed as to their exact function.
I mapped out the pins with my scope and traced them to the Motherboard.
As it turns out, the center pins of the 3 pin jumpers on the PC 7600 PCB (JUMP1 & JUMP2) are the RS232 "Transmit" and "Receive" lines from the Controller Motherboard. The signals on these center pins are then routed to the DB25 Female RS232 computer connector on Pins 2 & 3. These being the standard pins for RS232 transmit & receive.
The Jumper setting essentially determine weather pin 2 or pin 3 of the DB25 RS232 connector on the controller, are set as a "Transmit" or as a "Receive" pin.
This I'm assuming is due to the conversion from the older DB25 RS232 and the later DB9 RS232 where Pins 2 & 3 are inverted.
This allows the swapping of the two "Transmit" & "Receive" pins quickly if necessary using these 2 jumpers.
I will post my notes and some images tomorrow for the possible pin settings. I will upload them to the photos section so that we have this on file.
Hope this helps some of you,