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A Standard System Protocol
R-8
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
The PLC or host computer serving as the master sends a command and the component serving as the
slave returns a response for the command message contained in the command. One response mes-
sage is returned for each command message. The movement of command and response messages is
shown below.
Note In the following diagrams "Hex" indicates hexadecimal values. Values in quotation marks, such
as "00" indicate ASCII characters.
Command Frame
Response Frame
Note 1 Data is not saved in the response if there is a command frame error (i.e., if the end code is
not 00 or 0F).
2 Other values are possible for the subaddress and SID.
R-2-2 Communications Specifications
Item Specification
Transmission path con-
nections Multipoint
Communications RS-232C, RS-422A/485, 4-wire half-duplex, 2-wire half-duplex
Synchronization Start-stop
Baud rate 1,200/2,400/4,800/9,600/19,200/38,400 bps
Default: 9,600 bps
Transmitted code ASCII
Data length 7 bits or 8 bits (Default: 7 bits)
Note: A 7-bit code is used with 0 added to the beginning.
Stop bits 1 bit or 2 bits (Default: 2 bits)
Error detection Vertical parity (none, even, or odd) (Default: Even)
BCC (block check character)*
*: Start-stop Sync Data Configuration for Protocol Macros
LRC, 1 byte, equivalent to binary
R-2-3 Transmission Procedure
R-2-4 Command and Response Formats
Master (PLC or host computer)
Slave (component)
Command message
Response message
Node No.
Subaddress Command
Text
1 byte 2 bytes 2 bytes 1 byte 1 byte
1 byte
Data
"00" "0"
Node No.
Subaddress
End code Response
Text
1 byte 2 bytes 2 bytes 2 bytes
1 byte 1 byte
Data
(See note.)
"00"
"00"