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Appendix
A.1
Modbus
A.1.1
Modbus
Detailed information about Modbus can be found at the Modbus website (https://modbus.org/).
You can access the following measured variables:
• Via the Ethernet interface with the Modbus TCP protocol
• Via the PAC RS485 expansion module with the Modbus RTU protocol
More information
You can find further details about the PAC RS485 expansion module and Modus RTU in the
"PAC RS485 Expansion Module" equipment manual.
A.1.2
Function codes
Function codes control the data exchange. To do this, a function code tells the device what
action it is to take.
If an error occurs, the most significant bit (MSB) is set in the FC byte of the response frame.
Supported Modbus function codes
FC
0x01
0x02
0x03
0x04
0x05
0x06
0x0F
0x10
0x2B
0x14
PAC4220
Equipment Manual, L1V30827278B-01
Function in accordance with Modbus specification
Read Coils
Read Discrete Inputs
Read Holding Registers
Read Input Registers
Write Single Coil
Write Single Register
Write Multiple Coils
Write Multiple Registers
Read Device Identification
Read File Record (for average demand values)
A
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