Communication Status - Mitsubishi FX3U Series User Manual

FX Series Programmable Controllers
3U
User's Manual - MODBUS Serial Communication Edition
6.4

Communication status

The event and error counters will occupy ten devices beginning from the device defined by (D8415 / D8435)
and (D8416/D8436). PLC destination devices are latched, therefore the Master's devices will be cleared at
power ON and when the PLC is switched from STOP to RUN.
For Slave devices, the event and error counters will be cleared when: the communication is reset, a counter
reset command is received, at power ON and when the PLC is switched from STOP to RUN.
The following table shows the communication status of the event and error counters and the communication
event log data for the following scenario:
D8415 = 11H - i.e. store event counter and event log into D devices
D8416 = 100 - i.e. head device is set to D100
Device
Head Device
*1
(D100)
Head Device + 1
*1
(D101)
Head Device + 2
*1
(D102)
Head Device + 3
*1
(D103)
Head Device + 4
*1
(D104)
Head Device + 5
*1
(D105)
Head Device + 6
*1
(D106)
Head Device + 7
*1
(D107)
Head Device + 8
*1
(D108)
Head Device + 9
(D109)
Head Device + 10
*2
(D110)
Head Device + 11 to 42
*2
(D111-D142)
M: Master S: Slave
*1. Event and Error counters
*2. Communication event log
40
Description Valid
Bus Message
M, S
Counter
Bus Communication
M, S
Error Counter
Exception Error
M, S
Counter
Slave Message
S
Counter
Slave No Response
S
Counter
Slave NAK Counter S
Slave Busy Counter S
Character Overrun
M, S
Counter
Event counter S
Not used -
Event Log Length S
Event Log S
R: Read W: Write
6 Related Devices and Communication Status
Details
Number of messages that a remote node has
detected on the bus.
Note: Messages with false CRC/LRC are not taken
into account.
This counter is incremented if one of the following
errors occur:
• CRC/LRC mismatch
• Bit-level error (overrun, parity error)
• Received telegram length is <= 3 characters
(RTU) or <= 8 characters (ASCII)
Master: Number of received exception error
responses.
Slave: Number of exception conditions detected by
the remote node including exceptions
caused by broadcast messages (In this
case no exception response is sent).
Number of messages addressed to the slave
(including broadcast).
Number of received messages for which the slave
did not return a response (Number of received
broadcasted messages).
Number of times the slave responds with a NAK
exception (This is always 0 when using FX
Number of times the slave respond with a busy
exception (This is always 0 when using FX
Master: Number of times the master detected a
character overrun condition.
Slave: Number of times the slave detected a
character overrun condition.
This counter is incremented for each successful
message completion.It is not increased in the
following cases:
• Exception responses
• Poll commands
• Fetch event counter commands
-
Number of events stored in the event log.
Note: For details refer to Subsection 9.5.1.
Up to 64 events (Each D register = 2 events)
Note: For details refer to Subsection 9.5.1.
6.4 Communication status
R / W
R
R
R
R
R
R
.).
3U
R
.).
3U
R
R
-
R
R