Change Modbus Plus Address
Original instructions
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Description
Use MSTR Operation 17 (Change Modbus Plus Address) to change the Modbus Plus address associated with the embedded Modbus Plus port of the CPU.
On Low End CPUs, this function overrides the address switch (the hardware rotary switch behind the CPU) as long as the CPU is powered on. The address of hardware switch is restored when the CPU is restarted.
On High End CPUs, a new address set with this function is saved in the configuration table and is restored on subsequent CPUs starts.
Setting an address to a station that is already used by another station on the network disconnects the station already on the network and may cause unpredictable operation on the network.
CAUTION
UNINTENTIONAL EQUIPMENT OPERATION
Ensure that the Modbus Plus address to be set is not assigned to another station before using Operation 17.
Failure to follow these instructions can result in injury or equipment damage.
Network Implementation
The Operation 17 can only be performed for a Modbus Plus CPU embedded port. This operation is not available on the Modbus Plus ports of NOM modules.
Control Block
The following table describes the format of the Operation 17 Control Block:
Register
Meaning
Control[1]
17 (Change Modbus Plus Address operation)
Control[2]
Detected error status, see Modbus Plus, SY/MAX, and Ethernet TCP/IP Error Codes
Control[3]
16#1234
Control[4]
16#5678
Control[5]
16#00AA
Control[6
16#00BB
Control[7]
16#00CC
Control[8]
16#00DD
Control[9]
16#00EE
NOTE: The constant values in CONTROL[3] to CONTROL[9] consist of a signature that prevents unintentional use of this operation.
Data Buffer
The following table describes the format of the Operation 17 Data Buffer:
Register
Meaning
DADABUF[1]
Low byte: new address (range: 1 to 64)