Siemens SITRANS F Operating Instructions Manual page 31

Normal response
The normal response message contains the same slave address and function code as the
command message.
The Byte count is the number of data bytes returned in the response message. The number
is actually the quantity (in the command message) times 2, since there are two bytes of data
in each register.
The data section of the response message contains 8 upper and 8 lower bits of data for each
register that has been read from the device.
Table 6- 6
Message byte
Slave address
Function code
Byte count
Starting register
Next register
Last register
CRC-16
Exception response
The exception response message contains the same slave address as the command
message.
The function code of the exception message is actually a value of 80 hex plus the original
function code of 03 hex. The exception code indicates where the error occurred in the
command message. A complete listing of exception codes is shown in Exception handling
(Page 35).
Table 6- 7
Message byte
Slave address
Function code
Exception code
CRC-16
MAG 8000 Modbus RTU
Operating Instructions, 04/2016, A5E03409989-AB
Read multiple registers normal response messages
Upper
Lower
Upper
Lower
Upper
Lower
Lower
Upper
Read multiple registers exception response messages
Lower
Upper
Function codes
6.3 Read multiple registers
Example
xx hex
03 hex
xx hex
xx hex
xx hex
xx hex
xx hex
xx hex
xx hex
xx hex
xx hex
Example
xx hex
83 hex
01 hex to 06 hex
xx hex
xx hex
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