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Serial Communications Instructions Section 3-23
3-23-6 RECEIVE VIA SERIAL COMMUNICATIONS UNIT: RXDU(255)
Purpose Reads the specified number of bytes of data from one of the CJ-series Serial
Communications Unit’s serial ports.
Note A CJ Unit Adapter is required to use CJ-series Serial Communications Units.
This instruction can be used in the CP1H CPU Units only. It cannot be used in
the CP1L CPU Units. If RXDU(255) is used in a CP1L CPU Unit, Error Flag
(ER) will be turned ON.
Ladder Symbol
Variations
Applicable Program Areas
Operands The contents of the control words, C and C+1, are as shown below.
RXDU(255)
D
C
N
D: First destination word
C: First control word
N: Number of bytes
0000 to 0100 hex (0 to 256)
Variations Executed Each Cycle for ON Condition RXDU(255)
Executed Once for Upward Differentiation @RXDU(255)
Executed Once for Downward Differentiation Not supported.
Immediate Refreshing Specification Not supported.
Block program areas Step program areas Subroutines Interrupt tasks
OK OK OK OK
15 8 011 37 412
C
15 8 011 37 412
C+1
Destination unit address (See note.)
Serial Communications Unit's unit
address (unit number + 10 hex)
Serial port number
0: Specify directly. (See note.)
1: Port 1
2: Port 2
Port number specifier
(Internal logical port)
Specify 0 to 7 or F.
(F: Automatic allocation)
Always 00
Byte order
0: Most significant bytes first
1: Least significant bytes first
RS and ER signal control
0: No RS and ER signal control
1: RS signal control
2: ER signal control
3: RS and ER signal control
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