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RELAY OUTPUT CARD PCI
4.4 Programming Examples
Below are several simple examples using 80x86 assembly code for energizing and
checking the state of the reed relays on the Relay Output Card PCI. All examples
assume a base address of 300 Hex.
Example #1: Programming example to set Relay #27 on, write a “1” in bit position
D2, to port address Base+3, or 303 Hex.
MOV DX, 303H ;Set DX to Port D
MOV AL, 00001000B ;Set bit 3 to a ‘1’
OUT DX, AL
Example #2: Another method that takes into account the read-back capability of the
output ports.
MOV DX, 303H ;Set DX to Port D
IN AL, DX ;Get old port setting
NOT AL ;Invert bits - see note below
OR AL, 00001000B ;OR in bit 3
OUT DX, AL ;Set Bit 3
NOTE
Reading back the ports results in the binary complement of the output.
4.5 Register Description
Table 4-1. Registers.
Address Mode D7 D6 D5 D4 D3 D2 D1 D0
Base+0 R/W P1D7 P1D6 P1D5 P1D4 P1D3 P1D2 P1D1 P1D0
Base+1 R/W P2D7 P2D6 P2D5 P2D4 P2D3 P2D2 P2D1 P2D0
Base+2 R/W P3D7 P3D6 P3D5 P3D4 P3D3 P3D2 P3D1 P3D0
Base+3 R/W P4D7 P4D6 P4D5 P4D4 P4D3 P4D2 P4D1 P4D0
R/W = Read/Write bits
NOTE
The reed relay ports have a non-destructive readback capability.
Reading back the ports results in the binary complement of the output.
This is particularly useful when writing software that queries the last
value written to prevent inadvertently changing the state of the relays.