9600 Service Manual - gmecorp-usa.com

6 Workstation Control
U20 & 21, U12, 16, 17, & 19 are octal latches used to sink LED currents. Writing an "0"
to the appropriate bit will turn the addressed LED on. U20 & 21 are used to control the
LEDs on DS1 which is a diagnostic/status bargraph. U12, 16, 17, & 19 are used to
control the LEDs on the Track panel and the Front panel. R29, 30, 37, 36, 28, & 24 are
current limiting resistors for the LEDs.
Serial Communications
As the Control Panel Processor PCB receives instructions from the Keyboard, Front
Panel, and Track Pad panel, it sends data to the 386 AT Motherboard via U7, an RS232
serial transceiver. These signals then pass through the Auxiliary Interface PCB to the
AT Communications PCB where they are received by DUART U27. U27 then places the
information on the 386 AT Motherboard data bus. The Motherboard passes instructions
back through DUART U27 to the appropriate circuit board.
E2-E5 are jumpers to configure the serial communications signals for either RS422 or
RS232. They are presently configured for RS232.
Diagnostic Bargraph
DS1 is a diagnostic bargraph used to indicate various operating conditions in the
Workstation. Refer to the Workstation Software section for details.
Infrared Input
U9 is an opto-isolator that receives IR signals from the IR Receiver PCB. The output of
U9 passes through AND gate U3 and is then input to microcontroller U5 at pin 15. The
incoming infrared signals can be measured at test point TP5. Refer to the Infrared
Transmitter/Receiver heading in this section for details.