ICS PCI-16REL, User Manual

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Technical Description 3-3
Programming Examples
Below are two examples using 80X86 Assembly code for energizing and
checking the state of the reed relays on the PCI-16REL. Both examples
assume a base address of 300h:
Set Relay #3 on, write a ‘1’ in bit position D2, to port address Base+3, or 303h.
MOV DX, 303H ;Set DX to Port D
MOV AL, 00001000B ;Set bit 3 to a ‘1’
OUT DX, AL
Another method, which takes into account the read-back capability of output
ports C and D:
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 (C and D) results in the binary complement of the output
.