Diamond-MM-32DX-AT provides a 34-pin header on the left edge of the board labeled J4 for the 24 8255-type digital I/O lines. Pin 1 is in the lower left corner.
Note: The operation of digital I/O Latch and Ack signals is detailed in Chapter 16.
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Signal Name
Definition
A7 – A0
Digital I/O port A
B7 – B0
Digital I/O port B
C7 – C0
Digital I/O port C
Latch
Latch control input; active high
Ack
Acknowledge output for interrupt-based I/O; active high
RS-232 Rx/Tx
RS-232 transceiver terminals to communicate with onboard dsPIC
RS-485
Rx/Tx +/- RS-485 transceiver terminals to communicate with onboard dsPIC
+5V
Connected to PC/104 bus +5V power supply
Dgnd
Digital ground; connected to PC/104 bus ground
