----- Supply network analyzer CVM 96  Ethernet --------                          -----        Page  No.  36 
 
 
 
 
10.4.- MODBUS ©  protocol 
 
  The CVM 96 analyzer can communicate by means of the MODBUS © 
protocol, as it is following described:  
 
 When the CVM 96 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 
96. Each parameters is a 32-bits long, hence two words 
are required to inquiry for a parameter.  
  ( 4 bytes - XX XX XX XX ).  
 
FUNCTION  05                  Writing one relay