Rockwell Automation 900 Temperature Controller Communications Functions - Series B - Manual (Page 69)

Publication 900-UM004D-EN-E - July 2010
Modbus Communications Procedure 4-11
Reading Undisplayed Parameters
It is possible to read the parameters that are not displayed due to display
settings as well as the parameters that are never displayed in the Controller.
Example Command and Response
The following example shows the command/response when reading the
process value. (In this case, the slave address is H’01.)
Process Value in 4-Byte Mode
Address: H’0000; Read data: H’000003E8 (100.0 ° C)
Figure 4.9
Figure 4.10 Process Value in 2-Byte Mode
Write Variable Area
To write data to the variable area, set the required data in the command frame,
as shown in Figure 4.11.
Figure 4.11 Command Frame
•
Address: H’2000; Read data: H’03E8 (100.0
°
C)
Command:
Response:
01
01 03
03
02
20 00 00 01
03 E8
8FCA (CRC-16)
B8FA (CRC-16)
Number of
Elements
Slave
address
Function
code
Write
start address
Byte
count
1 1 2 2 1
H'10
2
CRC-16
0 to 208 (2 × 104)
Write data (for the
number of elements)