B&B Electronics RS-232 Digital Relay I/O 232DRIO User Manual
Page 13
232DRIO-0308 Manual
11
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used to specify which command will be executed by the
controller,either the “R” or “S” character. The set output command
requires one argument field (for normal environments) or two
argument fields (data and its complement for harsh environments).
This field contains the fourth and/or fifth data byte.
Command Syntax: ! or # 0
_
_ _
|
|
|
|
|
|
|
|
|
|
|
|
|
| ~Data Byte
|
| | Data
Byte
|
| Command
Byte
|
Address Byte
Start
of
Message
Byte
I/O Data Bytes
When constructing commands to manipulate output lines or
when reading the state of the I/O lines it is necessary to know how to
select and interpret the I/O data byte. The three I/O lines are
represented by one data byte.
A byte represents an eight-bit binary number (11111111),
therefore each byte can represent eight I/O lines. Each bit is
assigned a bit position and a weight (value). Refer to Table 3.3.
Table 3.3 – Bit Assignments for I/O Lines
Input
→ I #
Relay
→ R #
X
X
X
X
X
I
#1
R
#2
R
#1
Bit Position
7
6
5
4
3
2
1
0
Hex Weight
80
40
20
10
8
4
2
1
Decimal Weight 128 64
32
16
8
4
2
1
To set an output to a HIGH state the corresponding bit position
must be set to a "1". Conversely to set an output LOW the
corresponding bit position must be set to a "0". When reading I/O
lines, any bit set to a "0" indicates the corresponding I/O line is in
the LOW state and any bit set to a "1" indicates the corresponding
I/O line is in the HIGH state.