Specifications

57
Schneider Electric
The Modbus Protocol (continued)
Note: Function 13 has 43 sub-functions; Jbus uses only 6..
The Modbus protocol can be used to read
or write one or more bits, one or more
words, the contents of the event counter or
the contents of the diagnostic counters.
Frame structure Jbus Modbus
Diagnostic functions (sub-functions)
F8 Read diagnostic counters Read diagnostic counters
(01) Data = 0000 => no response
transmitted
data = FF00 resets counters
Response
no counter reset
(02-03-04-0A) Identical Identical
(0B) Count frames with no CRC
error
Count all frames
(0C-0D) Identical Identical
(0E) Not incremented upon
broadcast
Incremented upon broadcast
(0F) Count number of broadcasts
received
Count number of no-responses
from the slave
(10-11) Identical Identical
(12) Count character errors (format,
parity, etc.)
Count overruns
F11 Event counter.
Increments upon broadcast. In
the response the first word is
always at 0.
Event counter.
Not incremented upon
broadcast.
In the response the first word is
at 0 or FFFF (status)
F12 History of the last 64
exchanges.
In the response the first word is
always at 0..
History of the last 64
exchanges.
In the response the first word is
at 0 or FFFF (status).
Exception codes
(01-02-03-05-07-08) Identical Identical
(04) Device not ready Error during processing of the
query
(09) Overlapping of memory Not implemented
Extended functions (sub-functions)
F13 Program commands Program commands
(01 - 02) Identical Identical
(03 - 04) Address on 24 bits Address on 16 bits + 8 bits for
page number
Address extension
(25)
(26)
F14
Identical
Data byte = 00 or 80h
Identical
Identical
Data byte = 06h
Identical
Guide to Integration
Modbus / Jbus