User`s manual

40
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
6 Related Devices and Communication Status
6.4 Communication status
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
M: Master S: Slave R: Read W: Write
*1. Event and Error counters
*2. Communication event log
Device Description Valid Details R / W
Head Device
(D100)
*1
Bus Message
Counter
M, S
Number of messages that a remote node has
detected on the bus.
Note: Messages with false CRC/LRC are not taken
into account.
R
Head Device + 1
(D101)
*1
Bus Communication
Error Counter
M, S
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)
R
Head Device + 2
(D102)
*1
Exception Error
Counter
M, S
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).
R
Head Device + 3
(D103)
*1
Slave Message
Counter
S
Number of messages addressed to the slave
(including broadcast).
R
Head Device + 4
(D104)
*1
Slave No Response
Counter
S
Number of received messages for which the slave
did not return a response (Number of received
broadcasted messages).
R
Head Device + 5
(D105)
*1
Slave NAK Counter S
Number of times the slave responds with a NAK
exception (This is always 0 when using FX
3U.).
R
Head Device + 6
(D106)
*1
Slave Busy Counter S
Number of times the slave respond with a busy
exception (This is always 0 when using FX
3U.).
R
Head Device + 7
(D107)
*1
Character Overrun
Counter
M, S
Master: Number of times the master detected a
character overrun condition.
Slave: Number of times the slave detected a
character overrun condition.
R
Head Device + 8
(D108)
*1
Event counter S
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
R
Head Device + 9
(D109)
Not used - - -
Head Device + 10
(D110)
*2
Event Log Length S
Number of events stored in the event log.
Note: For details refer to Subsection 9.5.1.
R
Head Device + 11 to 42
(D111-D142)
*2
Event Log S
Up to 64 events (Each D register = 2 events)
Note: For details refer to Subsection 9.5.1.
R