Code Name Description
15 Return slave no
response count
The number of messages addressed to the slave for
which a response (neither a normal response nor an
exception response) has not been sent since its last
restart, clear counters operation or power up is returned
in the response.
16 Return slave NACK
response count
The number of messages addressed to the slave for
which a NACK response has been sent is returned in the
response.
18 Return bus
character overrun
count
The number of messages addressed to the slave for
which it has not been able to send a response due to a
character overrun since its last restart, clear counters
operation or power up is returned in the response.
Sending other subfunction codes than those listed above cause an
Illegal data value response.
The Modbus protocol provides the following diagnostic counters:
Table 5.1.15.1.-3 Diagnostic counters
Name Description
Bus message count The number of messages in the communications
system detected by the slave since its last pickup,
clear counters operation or power up.
Bus communication error count The number of CRC or LRC errors encountered by the
slave since its last restart, clear counters operation or
power up.
Bus exception error count The number of Modbus exception responses sent by
the slave since its last restart, clear counters operation
or power up.
Slave message count The number of messages addressed to the slave or
broadcast which the slave has processed since its last
restart, clear counters operation or power up.
Slave no response count The number of messages addressed to the slave for
which a response (neither a normal response nor an
exception response) has not been sent since its last
restart, clear counters operation or power up.
Slave NACK response count The number of messages addressed to the slave for
which a NACK response has been sent.
Bus character overrun count The number of messages addressed to the slave for
which it has not been able to send a response due to a
character overrun since its last restart, clear counters
operation or power up.
The following exception codes may be generated by the Modbus protocol:
90
REF610REF610
Feeder Protection Relay
Technical Reference Manual - ANSI Version
1MRS755535
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