Mitsubishi QJ71MB91, User Manual

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4
MODBUS(R) STANDARD FUNCTIONS
4.13 Get Communications Event Log (FC: 12)
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(a) Communications event log
When the slave (QJ71MB91) receives the Get communications event log (FC: 12)
from the master, it returns the data of the Communications event log area in the
buffer memory to the master.(address: 0F20
H
to 0F3F
H
/0F60
H
to 0F7F
H
)
* 1 The number of communications event logs can be confirmed only with the buffer memory.
It is different from the communications event counter value in the response message.
* 2 If the number of communications event logs exceeds 64, the oldest log is deleted and the latest log
is stored to Communications event log 0.
Communications event logs are stored in the buffer memory at the following
timing.
1) When receiving a request message
The slave (QJ71MB91) stores the communications event log before executing
the processing of the request message.
For the relevant communications event, "1" is stored.
Figure 4.77 Communications event log
Figure 4.78 Communications event at request message transmission
(L)
(L)
(L)
QJ71MB91 buffer memory (CH1)
New logs
Old logs
0F1F
H
(3871)
0F20
H
(3872)
0F21
H
(3873)
0F3F
H
(3903)
Communications event log count (0 to 64) *
1
Communications event log 0
Communications event log 1
Communications event log 2
Communications event log 3
Communications event log 62
Communications event log 63 *
2
(H)
(H)
(H)
1 0 0 0 1/0 1/0 1/0 1/0
b0 b1 b2 b3 b4 b5 b6 b7
Unused (Fixed to 0)
Communication error
Unused (Fixed to 0)
Bus character overrun error
In listen only mode
Broadcast message reception
Fixed to 1