4 - 3
4.1 MODBUS(R) Standard Function Support List
4
MODBUS(R) STANDARD FUNCTIONS
(Continued on next page)
Table4.1 MODBUS standard function support list (continued)
Function
code
(Sub code)
Sub-function
code
Function Description
Accessible
devices per
message
Broadcast Reference
08
16 Return slave NAK count
Reads out the number of NAK
responses to the master.
The QJ71MB91 always returns "0".
-
Section
4.11.12
17 Return slave busy count
Reads out the number of busy
responses to the master.
The QJ71MB91 always returns "0".
-
Section
4.11.13
18
Return bus character
overrun count
To the master, reads out the number of
times the request message size
exceeds the upper limit.
-
Section
4.11.14
19
Return IOP overrun
error count
Reads the IOP overrun error counter
value to the master.
The QJ71MB91 returns to the master
the number of times the request
message size exceeds the upper limit.
(Same as the Return bus character
overrun count)
-
Section
4.11.15
20
Clear overrun counter
and flag
Clears the overrun error counter and
flag.
The QJ71MB91 clears the character
overrun error counter value.
-
Section
4.11.16
11 -
Get communications
event counter
Acquires the number of messages
whose requested processing (read/
write, diagnostics, etc.) have been
normally completed.
Whether the action corresponding to the
request message is normally completed
or not can be checked.
-
Section
4.12
12 -
Get communications
event log
Acquires the communications event log
of the QJ71MB91 into the master.
-
Section
4.13
15 - Write multiple coils
Writes values (ON/OFF) to multiple
coils.
1 to
1968 points
Section
4.14
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