Omron SYSMAC CJ - REFERENCE MANUAL 01-2008 Reference Manual page 1035

Serial Communications Instructions
Description
996
Area
Index Registers
Indirect addressing
using Index Registers
RXD(235) reads data that has been received in no-protocol mode at the CPU
Unit's built-in RS-232C port or one of the Serial Communications Board's
serial ports (the port is specified with bits 8 to 11 of C) 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 A39206 for the CPU Unit's RS-232C port, A35606 for
Serial Communications Board port 1, or A35614 for Serial Communications
Board 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.
D
---
,IR0 to ,IR15
–2048 to +2047 ,IR0 to –2048 to +2047 ,IR15
DR0 to DR15, IR0 to IR15
,IR0+(++) to ,IR15+(++)
,–(– –)IR0 to, –(– –)IR15
Section 3-24
C N