Black Box IC908C, IC907C manual Programming Examples, Register Description, 1.Registers, Address

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.

10