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13.4 Write single register (0x06)
This function is used for writing a single holding register in the
slave. The request telegram specifies the address of the register
that is to be written. Register addresses start from zero, meaning
that a register numbered 10 is addressed as 9.
The normal response is an echo of the request, indicating that the
value was written.
Example of request from master to slave
In the request, the slave with address 1 is asked to write the
value of 0xAFFE to the register at address 0x1000.
Example of response from slave to master
The response is an echo of the request.
13.5 Write multiple registers (0x10)
This function is used for writing a block of contiguous holding
registers in the slave. Register addresses start from zero,
meaning that a register numbered 100 is addressed as 99.
Example of request from master to slave
In the request, the slave with address 1 is asked to write the
value of 0x0001 to the register at address 0x0020 and the value
of 0xB0B0 to the register at address 0x0021.
Example of response from slave to master
The response returns the function code, starting address and
quantity of registers written.
13.6 Diagnostics (0x08)
This function provides a test for checking the communication
system between the master and the Grundfos slave. It contains a
single-byte subcode to identify the test to be performed.
The following subcodes are supported:
Example of request from master to slave
The response is identical to the request.
Example of response from slave to master
Field Value
Address 0x01
Function code 0x06
Address HI 0x10
Address LO 0x00
Value HI 0xAF
Value LO 0xFE
Field Value
Address 0x01
Function code 0x06
Address HI 0x10
Address LO 0x00
Value HI 0xAF
Value LO 0xFE
Field Value
Address 0x01
Function code 0x10
Start address HI 0x00
Start address LO 0x20
Quantity HI 0x00
Quantity LO 0x02
Byte count 0x04
Register 33 HI 0x00
Register 33 LO 0x01
Register 34 HI 0xB0
Register 34 LO 0xB0
Field Value
Address 0x01
Function code 0x10
Start address HI 0x00
Start address LO 0x20
Quantity written HI 0x00
Quantity written LO 0x02
Subcode Name
0x00
Return query data
Data in this request are to be echoed in the
response. The response must be identical to the
request, so this function is often used to verify
Modbus communication.
0x01
Restart communications
All communication counters are cleared, and the
device is restarted.
0x02
Return diagnostics register
Returns the 16-bit diagnostics register. See section
13.7 Diagnostics register interpretation.
0x04
Force listen only
Forces the device into listen-only mode.
This effectively mutes the device, making it unable
to communicate on the network. To bring the device
back to normal mode, a "Restart communications"
command (code 0x08, subcode 0x01) must be
issued.
0x0A
Clear counters and diagnostics register
Clears all counters and the diagnostics register
(these are also cleared on power-up/restart).
0x0B
Return bus message count
Returns the number of messages detected by the
slave.
0x0C
Return bus CRC error count
Returns the number of CRC errors in the slave.
0x0D
Return bus exception count
Returns the number of Modbus exception responses
that the slave has transmitted.
0x0E
Return slave message count
Returns the number of messages that the slave has
processed.
0x0F
Return slave no response count
Returns the number of messages for which the
slave has sent no response.
0x12
Return bus character overrun count
Returns the number of overruns in the slave.
0x14
Clear overrun counter
Clears the overrun counter (this is also cleared on
power-up/restart).
Field Value
Address 0x01
Function code 0x08
Subcode 0x00
Data 0xAB
Data 0xCD
Field Value
Address 0x01
Function code 0x08
Subcode 0x00
Data 0xAB
Data 0xCD
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