Page 23 of 26
6 MODBUS RTU PROTOCOL
The CVM-MINI power analyzer communicates using the MODBUS© protocol. In the
MODBUS protocol the RTU (Remote terminal Unit) mode is used; each 8-bit per byte
in a message contains two 4-bits hexadecimal characters.
The format for each byte in RTU mode is:
Code 8 bit binary, hexadecimal 0-9, A-F.
2 hexadecimal characters contained in each 8-bit field in
the message.
Bits per byte 8 data bits.
Field Check-Error CRC Type (Cyclical Redundancy Check).
Modbus functions used:
Function 01 Reading the status of the relays.
Function 03 and 04 Reading n Words (16 bits-2 bytes). Function used for
reading the electrical parameters that the CVM-MINI is
measuring. All electrical parameters are long with 32 bits,
because of this two Words are required to request each
parameter.
(4 bytes - XX XX XX XX)
Function 05 Writing a relay.
6.1 MODBUS memory map