Omron CJ - REFERENCE MANUAL 07-2009 User Manual

13
Command/Response Formats Section 2-2
FCS Calculations The PLC calculates the FCS (Frame Check Sequence) value for each com-
mand frame it receives, and it checks for errors by comparing that value with
the FCS value sent with the command frame. The host computer must calcu-
late the FCS value when sending a command frame.
Also, when checking for errors in response frames, the host computer must
calculate the FCS value for each response frame it receives and compare that
value to the FCS value sent in the response frame.
Note The FCS is an 8-bit value converted into two ASCII characters. The 8-bit
value is the result of an exclusive OR sequentially performed between each
character in a transmission, from the first character in the frame to the last
character of the text in that frame. Non-ASCII data, however, may sometimes
be sent in the text data. If the data length is 7 bits, the leftmost bit of each
character is masked before the FCS is calculated.
Unit number
Header code
Text
FCS
Terminator
FCS calculation range
ASCII
Code
Calculation result
(See note.)
The value is converted to hexadecimal
and handled as ASCII.
@ 40 0100 0000
EOR
1 31 0011 0001
EOR
0 30 0011 0000
EOR
R 52 0101 0010
1 31 0011 0001
0100 0010
4 Hex
2 Hex
•
•
•

Omron CJ - REFERENCE MANUAL 07-2009 Specifications

General

Category	Computer Hardware
Manufacturer	Omron
Model	CJ
Document Type	REFERENCE MANUAL
Publication Date	07-2009

Summary

Manual Usage and Compliance

Warranty and Limitations of Liability

Outlines OMRON's product warranty terms and limitations of liability.

Precautions

Safety Precautions

Emphasizes critical safety measures for PLC use, including power handling and unit disassembly avoidance.

Operating Environment Precautions

Details precautions for PLC system operation in various environments to ensure reliability and prevent malfunction.

Application Precautions

Lists essential safety and operational precautions for PLC system applications, covering grounding and component handling.

Section 2: Overview of C-mode Commands

2-1 C-mode Commands

Explains C-mode (Host Link) commands as a serial communication system between PLC and host computer.

Section 3: Overview of FINS Commands

3-1 FINS Commands

Section 4: C-mode Commands

4-1 C-mode Command List

4-3 C-mode Command Details

Offers detailed descriptions of individual C-mode commands, including format, parameters, limitations, and execution conditions.