Information Technology Reference
In-Depth Information
Sub
function
Description
Query (data field)
Reply
00 00
Return query data
Same as the query.
Same as query.
00 01
Restart communication
option
00 00 (leave log as it
was prior to restart)
FF 00 (clear event
log)
Same as query.
00 02
Return diagnostic
register
00 00
Diagnostic 16-bit register contents.
The contents depends on the Modbus
type. An example is:
Bit
0 Continue on error
1 Run light failed
2 T-Bus test failed
3 Asynchronous bus test failed
4 Force listen mode
7 ROM Chip 0 test failed
8 Continuous ROM checksum test in
execution
9 ROM 1 test failed
10 ROM 2 test failed
11 ROM 3 test failed
00 03
Change ASCII input
delimiter
'
char
' 00
Change end-of-message character.
Return is the same as query.
00 04
Force listen only-mode
00 00
Slave goes into a listen-only mode
and thus does not respond.
00 0A
Clear counters and di-
agnostic register
00 00
Return is the same as query.
00 0B
Return bus message
count
00 00
Return is the same as query.
00 0C
Return bus communica-
tion error count
00 00
CRC Error count.
00 0D
Return bus exception
error count
00 00
Exception error count.
00 0E
Return slave message
count
00 00
Slave message count.
00 0F
Return slave no re-
sponse count
00 00
Slave no response count.
00 10
Return slave NAK
count
00 00
Slave NAK count.
00 11
Return slave busy count
00 00
Slave busy count.
00 12
Slave character overrun
count
00 00
Slave character overrun count.
00 13
Return overrun error
count
00 00
00 14
Clear overrun counter
and flag
00 00
00 15
Get/clear Modbus Plus
statistics
