Siemens SITRANS FC410 Operating Instructions Manual page 121

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
FC410 with Modbus
Operating Instructions, 02/2016, A5E33120874-AC
Modbus holding registers
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
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