Rockwell Automation 900 Temperature Controller Communications Functions - Series B - Manual (Page 67)

Publication 900-UM004D-EN-E - July 2010
Modbus Communications Procedure 4-9
Table 4.6
Name Description
Slave address Specify the 900-TCx’s unit number.
The unit number can be set between H’01 and H’63 hexadecimal
(1…99 decimal).
Function code The Read Variable Area function’s function code is H’03.
Read start address Specify the address containing the data to be read.
Refer to Chapter 5 Communications Data for Modbus for
details on addresses.
Number of elements Specify 2 times the number of setting data items as the number
of elements to be read. The setting range for the number of
elements is H’0002…H’006A (2…106).
When H'006A is set, 53 items of setting data can be read.
Example: When reading 2 items of setting data, set the number
of elements to H’0004.
2-byte Mode
Specify the number of setting data items to be read as the
number of elements.
The setting range for the number of elements is H'0001…H'006A
(1…to 106).
When H'006A is set, 106 items of setting data can be read.
Example: When reading two items of setting data, set the
number of elements to H'0002.
CRC-16 This check code is calculated with the data from the slave
address to the end of the data.
For details on the CRC-16 calculation, refer to CRC-16 Calculation
Example in on page 5-2.