Preset Single Register (Function Code 06)
Query
This Function Code allows you to modify the contents of a Modbus 4x range in the
slave. This code writes to one register only. Any holding register that exists
within the controller can have its contents changed by this message. However,
because the controller is actively scanning, it can also alter the content of any
holding register at any time. The values are provided in binary up to the maximum
capacity of the controller. Unused high-order bits must be set to zero.
When used with slave address zero (Broadcast mode), all slave controllers load the
specified register with the contents specified.
TIP:
Functions 5, 6, 15, and 16 are the only
messages that are recognized as valid for broadcast. This is the structure of
the message being sent out to the Modbus network. The following byte values are
displayed in hexadecimal format.
The following example is a request to write the value ‘3’ to register 40002 in slave
11.
Node Address
| Function Code
| Data Start Bit High
| Data Start Bit Low
| Preset Data Register High
| Preset Data Register Low
| Error Check Field (2 bytes)
|
0B | 06 | 00 | 01 | 00 | 03 | CRC |
Response
The response to a preset single register request is to retransmit the query message
after the register has been altered.
Node Address
| Function Code
| Data Register High
| Data Register Low
| Preset Data Register High
| Preset Data Register Low
| Error Check Field (2 bytes)
|
0B | 06 | 00 | 01 | 00 | 03 | CRC |
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