Siemens SITRANS F Series Operating Instructions Manual page 89

Function code 16 (Write multiple registers)
General exceptions
• Writing less than 1 or more than 16 registers => Exception 3 (Illegal data value)
• If ByteCount is not exactly 2 times NoOfRegisters => Exception 3 (Illegal data value)
• Requesting invalid start address or start address with invalid quantity => Exception 2 (Illegal
data address)
Application exceptions:
• Application errors; min/max limit of parameter exceeded; or parameter write-protected =>
Exception 4 (Slave device error)
• Application errors include writing to ReadOnly holding registers
Holes/register alignment:
• If start-address is not the start of a mapped holding register => Exception 2 (Illegal data
address)
• Writing to holes is allowed (ie ignored - and no exception occurs) - except for the condition
described above
• If the end address is only part of a mapped holding register item (e.g. one half of a float
value), the action depends on the data type. Writing parts of all data types => Exception 4
(Slave device error)
Function code 16 example
Query
Slave address
Function
Starting Address Hi
Starting Address Lo
Quantity of Registers Hi
Quantity of Registers Lo
Byte Count
Registers Value Hi
Registers Value Lo
:
Registers Value Hi
Registers Value Lo
CRC
Response
Slave address
Function
Starting Address Hi
SITRANS FST090
Operating Instructions, 11/2021, A5E50387341-AA
A.2 Modbus function codes
1 byte
1 byte
1 byte
1 byte
1 byte
1 byte
1 byte
1 byte
1 byte
:
1 byte
1 byte
2 bytes
1 byte
1 byte
1 byte
Modbus communication
89