834
Serial Communications Instructions Section 3-23
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.)
Operand Specifications
Description RXDU(255) reads data that has been received in no-protocol mode at the
Serial Communications Unit with the unit address specified in bits 0 to 7 of
C+1, through the port specified with bits 8 to 11 of C+1, and stores that data
starting at D. If fewer than N bytes of data have been received at the port, then
only the data that has been received will be stored. The logical port number
can be set to any value between 0 and 7 and is specified with bits 12 to 15 of
C+1.
Execute RXDU(255) to read the received data from the buffer when the
Reception Completed Flag (in the allocated DM Setup Area) is ON.
Up to 259 bytes can be received, including the receive data (N = 256 bytes
max.), the start code, and the end code.
The following diagram shows the order in which data is received and the con-
tents of the receive frame for various settings.
Note The logical port number can be allocated automatically by setting bits 12 to 15
of C+1 to F. For details, refer to About Communications Port Numbers on
page 850.
Area DCD
CIO Area CIO 0 to
CIO 6143
CIO 0 to
CIO 6142
CIO 0 to
CIO 6143
Work Area W0 to W511 W0 to W510 W0 to W511
Holding Bit Area H0 to H511 H0 to H510 H0 to H511
Auxiliary Bit Area 448 to A959 A0 to A958 A0 to A959
Timer Area T0000 to T4095 T0000 to T4094 T0000 to T4095
Counter Area C0000 to C4095 C0000 to C4094 C0000 to C4095
DM Area D0 to D32767 D0 to D32766 D0 to D32767
Indirect DM addresses
in binary
@ D0 to @ D32767
Indirect DM addresses
in BCD
*D0 to *D32767
Constants --- Specified values
only
#0000 to #0100
(binary) or &0 to
&256 (decimal)
Data Registers --- --- DR0 to DR15
Index Registers ---
Indirect addressing
using Index Registers
,IR0 to ,IR15
–2048 to +2047 ,IR0 to –2048 to +2047 ,IR15
DR0 to DR15, IR0 to IR15
,IR0+(++) to ,IR15+(++)
,–(– –)IR0 to, –(– –)IR15
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