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MELSEC-F
WHEN COMMUNICATING DATA USING THE MC PROTOCOL9
9 - 39
9.5 Loopback Test
A loopback test checks whether or not the communication function between an
external device and the Ethernet module operates normally. The examples show the
control procedure using this function.
9.5.1 Loopback test (command: 16)
The examples shown in this section explain the control procedure for an external
device performing a loopback test with the Ethernet unit.
The order and content of data items of the areas marked by " " shown in the control
procedure diagram differ depending on the module used as well as the frame and
format used for communication.
See the detailed information described in Subsection 9.1.2.
[Control procedure]
(1) Performing a loopback test while communicating in binary code
POINT
(1) A loopback test checks whether or not the connection between the external
device and the Ethernet module is correct and that the data communication
function operates properly when the FX
3U-ENET-L is started up or when a
problem occurs.
(2) Use the following data for loopback tests.
Send the head part first.
• When communicating in binary code
Maximum of 254 bytes of numerical values (00 to FF
H).
• When communicating in ASCII code
Maximum of 254 single-byte characters ("0" to "9", "A" to "F").
(Data name)
External device
side
(Example)
(Data name)
(Example)
PLC side
Subcommand
PC No.
Monitoring
timer
Complete code
Subcommand
16
H
FF
H
0A
H
00
H
LH
96
H
00
H
Data length
(1 to 254 bytes)
Head send data
Second send data
Last send data
Data length
(1 to 254 bytes)
Head send data
Second send data
Last send data
Designated byte length+5bytes
Designated byte length+3bytes