Contents
6.1
6.1.1
COMMREQ Function Example .................................................................................................................................... 202
6.1.2
Timing .................................................................................................................................................................................... 202
6.1.3
6.1.4
6.1.5
6.1.6
6.2
Serial I/O Protocol ............................................................................................................. 208
6.2.1
6.2.2
Compatibility ...................................................................................................................................................................... 208
6.2.3
6.2.4
Serial I/O COMMREQ Commands ............................................................................................................................. 210
6.2.5
Overlapping COMMREQs .............................................................................................................................................. 211
6.2.6
Initialize Port Function (4300) .................................................................................................................................... 212
6.2.7
6.2.8
6.2.9
Read Port Status Function (4303) ............................................................................................................................ 215
6.2.10
6.2.11
Cancel COMMREQ Function (4399) ......................................................................................................................... 218
6.2.12
Autodial Function (4400) .............................................................................................................................................. 219
6.2.13
Write Bytes Function (4401) ....................................................................................................................................... 221
6.2.14
Read Bytes Function (4402) ........................................................................................................................................ 222
6.2.15
Read String Function (4403) ....................................................................................................................................... 224
6.3
RTU Slave Protocol ........................................................................................................... 226
6.3.1
Message Format ............................................................................................................................................................... 227
6.3.2
Cyclic Redundancy Check (CRC) ................................................................................................................................ 232
6.3.3
RTU Message Descriptions .......................................................................................................................................... 236
6.3.4
RTU Scratch Pad ............................................................................................................................................................... 252
6.3.5
Communication Errors .................................................................................................................................................. 253
6.3.6
6.4
SNP Slave Protocol ........................................................................................................... 257
6.4.1
Permanent Datagrams .................................................................................................................................................. 257
6.4.2
Appendix A Performance Data ........................................................................................................... 259
A-1 Boolean Execution Times ............................................................................................................. 260
A-2 Instruction Timing ......................................................................................................................... 261
A-2.1
Overview .............................................................................................................................................................................. 261
PLC Version Information ............................................................................................................................................... 262
iv
PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual
GFK-2222AD