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User Manual
PROFINET / Modbus TCP Master
Document code: MN67611_ENG Revision 1.001 Page 20 of 29
MODBUS DIAGNOSTIC OVER PROFINET:
During the normal functioning of the device, if all the programmed Modbus requests have received a valid reply (not an exception error),
every PROFINET frame has the "Data Status" byte at the value of 0x35.
Otherwise, if at least one Modbus reply is not valid, the "Data Status" byte assumes the value 0x15; that means "Problem Indicator".
Moreover, it is possible to save the Modbus Diagnostic on Output PROFINET array using the field “Diagnostic” of the section “Set
Communication”.
In this case, the status of each Modbus request defined in the section “Set Access” is saved starting from the byte of the PROFINET array
defined in the section “Set Communication”.
Each bit will represent the status of a Modbus request:
If for a request the converter receives a correct response, the status bit is put to ‘0’;
If for a request the converter receives a wrong response or it doesn’t receive any response, the status bit is put to ‘1’.
Example:
In the section “Set Access” are defined 8 Modbus reading requests (“Modbus Read” table) and 8 Modbus writing requests (“Modbus Write”
table). The Modbus reading requests are working and the Modbus writing request are not working.
The status bits of the Modbus Diagnostic on PROFINET will be:
Byte x
Byte x+1
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
bit7
bit6
bit5
bit4
bit3
bit2
bit1
bit0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
where ‘x’ is the starting byte of the PROFINET array where the Modbus diagnostic is saved.
