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
Table 3.3 – Bit Assignments for I/O Lines
Input → I # |
|
|
|
|
| I | R | R |
Relay → R # | X | X | X | X | X | #1 | #2 | #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.
11 | |
B&B Electronics | PO Box 1040 |
PH (815) | |