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----- Supply network analyzer CVM-144 ------ User's manual --- Page No. 48

11.4.- MODBUS © protocol

The CVM-144 analyzer can communicate by means of the MODBUS ©

protocol, as it is following described:

When the CVM-144 communicates with MODBUS protocol, it uses the RTU

mode (Remote Terminal Unit ). Each 8-bits byte in a message contains two 4-bits

hexadecimal characters.

The format for each byte in RTU mode is :

* Code : 8-bits binary, hexadecimal 0-9, A-F

Two hexadecimal characters

contained in each 8-bits field of the

message.

* Bits per Byte : 8 data bits

* Error Check Field : Cyclical Redundancy Check ( CRC ) .

MODBUS FUNCTIONS:

FUNCTION 01 Reading of relay state

FUNCTION 3 or 4 Reading of n Words (16 bits-2 bytes). This function

permits to read all the electrical parameters of the

CVM-144. Each parameters is a 32-bits long, hence

two words are required to inquiry for a parameter.

FUNCTION 05 Writing one relay

1 2 ... 44 45 46 47 48 49 50 51 52 53 54 ... 57 58

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Circutor CVM144 Series Manuale Utente Pagina 49