821
Serial Communications Instructions Section 3-23
Description RXD(235) reads data that has been received in no-protocol mode at a serial
port on a Serial Communications Option Board and stores N bytes of data in
words D to D+(N
÷2)–1. If N bytes of data has not been received at the port,
then only the data that has been received will be stored.
Data can be received only when the port’s Receive Ready Flag is ON. The
Receive Ready Flag is A392.14 for serial port 1 and A396.06 for serial port 2.
Execute RXD(235) only when the corresponding Receive Ready Flag 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 Serial port 1 is the port on the Serial Communications Option Board mounted
in option slot 1 and serial port 2 is the port on the Serial Communications
Option Board mounted in option slot 2.
Counter Area C0000 to C4095
DM Area 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
Area DCN
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