Batch Controller RA33 Commissioning
Endress+Hauser 39
Transmission of values
The actual Modbus TCP protocol is between Layers 5 and 6 in the ISO/OSI Model.
To transmit a value, 3 registers of 2 bytes each are used (2 bytes status + 4-byte float). In the setup,
you can configure which register is to be written with which value. The most important/most com-
mon values are already preconfigured.
Validity and limit value information are encoded in the status byte.
On receipt of the request from the master, the required start register and the number of registers to
be read are sent to the batch controller. Because a measured value always requires three registers,
the start register and the number must be divisible by 3.
From the master to batch controller:
ga fk r1 r0 a1 a0 c1 c2
Response from the batch controller for successful request:
ga fk az s1 s0 w3 w2 w1 w0 s1 s0 w3 w2 w1 w0 . . . . . s1 s0 w3 w2 w1 w0 c1 c0
Response from Batch Controller for unsuccessful request:
ga fk fc c0 c1
Register 000 Status of first measured value (16-bit integer, high byte first)
Register 001 to 002 First measured value (32-bit float, high byte first)
16 654321
not used 0000ok
0001Open circuit
0010Over range
0011Under range
0100Invalid measured value
0110Replacement value
0111Sensor error
1 Lower limit value violated
1 Upper limit value violated
1 Counter overflow
ga Slave address (1 to 247 )
fk Function, always 03
r1 r0 Start register (high byte first)
a1 a0 Number of registers (high byte first)
c0 c1 CRC checksum (low byte first)
ga Device address
fk Function, always 03
az Number of bytes of all subsequent measured values
s1 s0 Status of first measured value (16-bit integer, high byte first)
w3 w2 w1 w0 First measured value in 32-bit float format, high byte first
s1 s0 Status of second measured value (16-bit integer, high byte first)
w3 w2 w1 w0 Second measured value (32-bit float, high byte first)
s1 s0 Status of last measured value (16-bit integer, high byte first)
w3 w2 w1 w0 Last measured value (32-bit float, high byte first)
c0 c1 CRC checksum, 16-bit (low byte first)
ga Device address
fk Requested function + 80hex
fc Error code
c0 c1 CRC checksum, 16-bit (low byte first)
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