C-Mode Commands - Omron CJ - REFERENCE MANUAL 07-2009 Reference Manual

C-mode Commands

2-1 C-mode Commands
C-mode command
8
C-mode (Host Link) commands form a command/response system for serial
communications (Host Link Mode) to perform various control operations
between a CPU Unit and a host computer directly connected to it. These
operations include reading from and writing to I/O memory, changing operat-
ing modes, executing forced set and forced reset operations, and so on.
Response
1. There are two Host Link formats: the 1:N Host Link (with N ≥ 1) and the 1:1
Note
Host Link.
• The 1:1 Host Link is the earlier Host Link format supported by C-series
PLCs, such as the C200H, C1000H, and C2000H.
• The built-in peripheral and RS-232C ports of CS/CJ-series CPU Units,
built-in serial ports of N-type CP1E CPU Units, serial port C on NSJ
Controllers, and serial ports 1 and 2 on the Option Board for CP-series
CPU Units support only the 1:N Host Link format. When a Serial Com-
munications Board or Unit (version 1.2 or later) is being used, a 1:1
Host Link program created for a C-series PLC (C200H/C1000H/
C2000H) can be reused by selecting the Host Link 1:1 format.
In this manual, the term "Host Link" generally indicates the 1:N Host Link.
2. Unlike FINS commands, C-mode commands can only be addressed to a
CPU Unit, and they cannot be used for message service outside of the lo-
cal network. They cannot be used for functions such as file operations.
C-mode (Host Link) commands can be sent from a host computer connected
to a CS/CJ-series Host Link Unit. Up to 32 PLCs (Host Link Units) can be con-
nected to a single host computer. For identification, each Host Link Unit is
assigned a unit number from 0 to 31.
The length of a single unit of a command or response exchange is called a
"frame." A single frame contains a maximum of 131 characters of data. Char-
acters are sent and received as ASCII.
Note For a CS/CJ-series PLC, a "Host Link Unit" can be the CPU Unit, a Serial
Communications Unit, or a Serial Communications Board.
A maximum of 30 words of data can be transferred for the first command
frame and a maximum of 31 words of data can be transferred for other com-
mand frames when reading or writing word data in I/O memory. When read-
ing/writing more than 30 words of data, the data transfer will be processed in
multiple transmissions, with 30 words in the first and up to 31 words in each of
Response
C-mode command
Section 2-1