ABB M101 - Data Presentation for Function Codes 03 and 04; Function Code 06 - Preset Single Register; Function Code 08 - Preset Single Register

FUNCTION CODES DATA PRESENTATION FOR FUNCTION CODE 03
AND 04
1TGC908004M0201 41
8.5. Data Presentation for Function Code 03 and 04
Function code 03 and 04 using a 16 bit modbus register. In the first byte of register is high
part of data in second byte is the low data part.
Bit Number
15
-
8
7
-
0
Register n
Data High
Data Low
Table 16 Byte representation for function code 03 and 04
A float value has 4 bytes and uses two 16-bit Modbus registers. See following table:
Bit Number 15 - 8 7 - 0
Register n
Data High
Data Low
Register n+
1
Data Low
-
High
Data Low
-
Low
Table 17 Byte representation for Float
In case Mapping Tool parameter “Float Register Big Endian” is set to “No” data presentation
of float value is as follows:
Bit Number
15
-
8
7
-
0
Register n
Data Low
-
High
Data Low
-
Low
Register n+
1
Data High
-
High
Data High
-
Low
Table 18 Byte representation for Float Big Endian
8.6. Function Code 06 – Preset Single Register
Function code 06 allows control system to modify the contents of a single output register.
Any output register that exists within the system can have its contents changed by this mes-
sage i.e.
Switching Commands, other commands
• The valid address range: 40001-49999
Outgoing commands utilizing FC06 are always sent, regardless of any change to the
command value.
8.7. Function Code 08 – Preset Single Register
The purpose of the loop back test is to test the communication between Master and Slave
station. The data passed in the request data field is returned (looped back) in the response
(Sub-function 0000). The entire response message should be identical to the request.