Rockwell-automation 900 Temperature Controller Communications Function Manual de usuario descargar pdf (Pagina 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 03

20 00 00 01

03 E8

8FCA (CRC-16)

B8FA (CRC-16)

Number of

Elements

Slave

address

Function

code

Write

start address

Byte

count

11 2 21

H'10

CRC-16

0 to 208 (2 × 104)

Write data (for the

number of elements)

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 102 103

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Rockwell-automation 900 Temperature Controller Communications Function Manual de usuario Pagina 69