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ASCII Serial Port Instructions (ABL, ACB, ACL, AHL, ARD, ARL, AWA, AWT)
ASCII Chars in Buffer (ACB)
Chapter 17
The ACB instruction counts the characters in the buffer.
Operands:
Relay Ladder
ACB
ASCII Chars in Buffer
Channel
SerialPort Control
Character Count
EN
DN
?ER
?
Operand
Type
Format
Enter
Channel
DINT
immediate
0
tag
?
Serial Port
SERIAL_PORT_
Control
CONTROL
Character
Count
DINT
tag
tag that controls the operation
immediate
0
During execution, displays the number of
characters in the buffer.
Structured Text
ACB(Channel
SerialPortControl);
The operands are the same as those for the relay ladder ACB instruction.
However, you specify the Character Count value by accessing the .POS
member of the SERIAL_PORT_CONTROL structure, rather than by
including the value in the operand list.
SERIAL_PORT_CONTROL Structure
Mnemonic
Data Type
Description
.EN
BOOL
The enable bit indicates that the instruction is enabled.
.EU
BOOL
The queue bit indicates that the instruction entered the ASCII queue.
.DN
BOOL
The done bit indicates when the instruction is done, but it is asynchronous to the logic scan.
.RN
BOOL
The run bit indicates that the instruction is executing.
.EM
BOOL
The empty bit indicates that the instruction is done, but it is synchronous to the logic scan.
.ER
BOOL
The error bit indicates when the instruction fails (errors).
.FD
BOOL
The found bit indicates that the instruction found a character.
.POS
DINT
The position determines the number of characters in the buffer, up to and including the first
set of termination characters.
.ERROR
DINT
The error contains a hexadecimal value that identifies the cause of an error.
Publication 1756-RM003K-EN-P - July 2008
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