1013
Serial Communications Instructions Section 3-24
3-24-6 RECEIVE VIA SERIAL COMMUNICATIONS UNIT: RXDU(255)
Purpose Reads the specified number of bytes of data from one of the Serial Communi-
cations Unit’s serial ports. (The Serial Communications Unit must be Ver. 1.2
or later).
Ladder Symbol
Variations
Applicable Program Areas
Operands The contents of the control words, C and C+1, are as shown below.
Note The serial port’s unit address can be specified directly by setting the serial
port number to 0 and setting the destination unit address to the serial port’s
unit address. (Set the destination unit address to 80 hex + 4
× unit number for
port 1 or 81 hex + 4
× unit number for port 2.)
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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