FX communication
Commands 8
8-21
8
8.11 Loopback Test
The loopback test is the function for testing if communication between the computer and
programmable controller is operating as normal or not.
1 ) Command Specification
Protocol format 1 is shown.
2 ) Specification example
To test the Loopback with data “ABCDE” at station No.0 (with message wait time set to 0 ms)
Computer
Programmable
controller
E N Q
Station
No.
PLC No.
T T
Message
wait time
Sum check
code
Station
No.
S T X
PLC No.
Data
(same data
as character
A area)
E T X
Sum check
code
Character area B
Loopback test command
Data
(designated
No.
characters)
2 characters (hexadecimal)
Character area A
2 characters (hexadecimal)
No.
Character
No.
Characters
Notes
• Specify the number of characters so as to satisfy the following condition.
-1
≤
No.characters
≤
254 (25 for FX
0N
)
• The station number, PC (PLC) number, number of devices, and sum check code are
expressed in hexadecimal.
Computer
Programmable
controller
E
N
Q
The sum check is calculated
over this range
30H30H
0 0
46H46H
F F
54H54H
T T
30H
0
41H 45H44H43H42H 38H37H
A B C D E 7 8
05H
S
T
X
30H30H
0 0
46H46H
F F
02H
E
T
X
33H
41H
A 3
03H
35H30H
0 5
41H 45H44H43H42H
A B C D E
35H30H
0 5
Same data is transmitted.
The sum check is calculated over
this range
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