User`s manual

FX communication
Computer link 7
7-6
7.4.1 Control Protocol Format 1
Description Control protocol
To read data
from the PLC
to the
computer
To write data
from the
computer to
the
PLC
Remarks
1 ) Sum check code is used when the sum check flag is set “Yes” (“b13=1” in special data register
D8120), and not used when set to “No” (“b13=0”).
2 ) When the sum check flag is set to “Yes”, the sum check is made on the characters in the
asterisked area.
3 ) In the diagram, the contents of character area A, character area B, and character area C
depend on the individual system, but do not differ depending on the format of control protocol.
For details of each character area, see the link contents.
Computer
Programmable
controller
E N Q
Station
No.
PLC No.
Command Message wait time
Character
area A
Sum
check
code
Station
No.
S T X
PLC No.
Character
area B
E T X
Sum
check
code
Station
No.
A C K
PLC No.
Station
No.
N A K
PLC No.
or
N A K
Station
No.
PLC No.
Error
code
or
*
*
Transmission sequence
Computer
Programmable
controller
E N Q
Station No. PLC No.
Command Message wait time
Character
area C
Sum check
code
Station No.
A C K
PLC No.
N A K
Station No. PLC No. Error code
or
*
Transmission sequence