Siemens SINAMICS V20 Operating Instructions Manual page 183

FC16 - Write Multiple Registers
When a message with FC = 0x10 is received, then 5 + N bytes of data are expected, that is,
FC16 has 5 + N bytes of data:
● 2 bytes for the starting address of register
● 2 bytes for the number of registers
● 1 byte for the byte count
● N bytes for the register values
Byte 1 Byte 2 Byte 3
Address FC Start address
(0x10)
High
Converter response
Byte 1 Byte 2
Address FC (0x10)
Acyclic communication via MODBUS
Acyclic communication or general parameter access is realized using the Modbus registers
40601 ... 40722.
Acyclic communication is controlled using 40601. 40602 contains the function code (always
= 47 = 2F hex) and the number of the following user data. User data are contained in
registers 40603 ... 40722.
Overview of acyclic communication
40601
Error codes
1 hex: Invalid Length (invalid length)
2 hex: Invalid State (in the actual converter state, this action is not permitted)
3 hex: Invalid function code (FC ≠ 2F hex)
4 hex: Response not ready (the response has still not been issued)
5 hex: Internal Error (general system error)
Incorrect access operations to parameters via data set 47 are logged in registers
40603 ... 40722.
SINAMICS V20 Converter
Operating Instructions, 10/2019, A5E34559884-012
Byte 4 Byte 5
Number of regis-
ters
Low High
Byte 3 Byte 4
Start address
High Low
Value in the register
40602
0 47
1 47 Request length [bytes]
2 47 Response length [bytes]
2 47
Byte 6 Byte 7 ...
Number ...
of bytes
Low
Byte 5
Number of registers
High
40603 ... 40722
... ...
Request data
Response data
0 Error code
Communicating with the PLC
7.2 MODBUS communication
Byte N - 1 Byte N Byte N + 1
Register N value CRC
High Low High
Byte 6 Byte 7
CRC
Low High
Explanation
Write values for acyclic access
Activate acyclic access
Response for a successful request
Response for an erroneous request
Byte N + 2
Low
Byte 8
Low
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