Siemens SITRANS F Modbus RTU RS 485 - Page 27

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 Read multiple registers normal response messages
Message byte Example
Slave address xxhex
Function code 03hex
Byte count xxhex
Starting register Upper xxhex
Lower xxhex
Next register Upper xxhex
Lower xxhex
Last register Upper xxhex
Lower xxhex
CRC-16 Lower xxhex
Upper xxhex
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 03hex. The exception code indicates where the error occurred in the command
message. A complete listing of exception codes is shown in a later chapter.
Table 6-7 Read multiple registers exception response messages
Message byte Example
Slave address xxhex
Function code 83hex
Exception code 01hex to 06hex
CRC-16 Lower xxhex
Upper xxhex
Examples
Read absolute mass 󹪞ow (4:03001)
• Query: 1,3,11,184,0,2,70,10 (Hex 01,03,0B,B8,00,02,46,0A)
• Response: 1,3,4,64,195,82,139,98,200 (Hex 01,03,04,40,C3,52,8B,62,C8)
• Absolute mass 󹪞ow = 6.10383 kg/sec.
Read absolute density (4:03005)
• Query: 1,3,11,188,0,2,7,203 (Hex 01,03,0B,BC,00,02,07,CB)
• Response: 1,3,4,68,54,162,145,182,1 (Hex 01,03,04,44,36,A2,91,B6,01)
• Absolute density = 730.54010 kg/m3
Functions codes
6.3 Read multiple registers
Modbus RTU RS 485
Operating Instructions, 03/2021, A5E00753974-AB 27