B&B Electronics RS-485 manual Reading Digital I/O Command, AddrRD, States

Reading Digital I/O Command

The Read Digital I/O command returns a byte which represents the states of the 3 digital input and 3 digital output states. Bits 3-5 correspond to the states of digital inputs 0-2. Bits 0-2 correspond to the states of digital outputs 0-2. If a bit is a 0 then the digital state of that digital I/O is LOW. If a bit is a 1 then the digital state of the I/O is HIGH. Refer to Table 3.4 and 3.5.

Command Syntax

!{addr}RD

Unit Response

{states}

Where {states} is a byte in which Bits 0-2 corresponds to the current states of Digital Outputs 0-2 and Bits 3-5 corresponds to the current states of Digital Inputs 0-2.

Table 3.4 - Read Digital I/O Response for Outputs

	Response Byte				Digital Outputs
Bit 2		Bit 1	Bit 0	#2		#1	#0
0		0	0	LOW		LOW	LOW
0		0	1	LOW		LOW	HIGH
0		1	0	LOW		HIGH	LOW
0		1	1	LOW		HIGH	HIGH
1		0	0	HIGH		LOW	LOW
1		0	1	HIGH		LOW	HIGH
1		1	0	HIGH		HIGH	LOW
1		1	1	HIGH		HIGH	HIGH
	Table 3.5 - Read Digital I/O Response for Inputs
	Response Byte				Digital Inputs
Bit 5		Bit 4	Bit 3	#2		#1	#0
0		0	0	LOW		LOW	LOW
0		0	1	LOW		LOW	HIGH
0		1	0	LOW		HIGH	LOW
0		1	1	LOW		HIGH	HIGH
1		0	0	HIGH		LOW	LOW
1		0	1	HIGH		LOW	HIGH
1		1	0	HIGH		HIGH	LOW
1		1	1	HIGH		HIGH	HIGH
485SDA103798 Manual							15

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