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485SDA103798 Manual 15
B&B Electronics -- 707 Dayton Rd. -- PO Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 434-7094
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