B&B Electronics 232DRIO manual Bit Assignments for I/O Lines, Data Bytes

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 #						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.

232DRIO-0308 Manual	11
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