Sunfar E500-2S0022(B) - Page 98

88 MODBUS Protocol
E500 Series Universal Low-Power Inverter
Objection code indicates error category:
Objection code Corresponding error
01 Illegal function code
02 Illegal data address
03 Overhanging data
04 Invalid operation of slave machine
20 Too much read-write parameters
21 Reserve read-write, implicit parameter
22 Slave machine running forbids modifying data
23 Data modification is protected by password
24 Failure in read-write parameter
CRC CHECK:
CRC CHECK CRC Low CRC High
Data length (Byte) 1 1
CRC CHECK function is shown as below:
unsigned int crc_chk_value(unsigned char *data_value, unsigned char length)
{
unsigned int crc_value=0xFFFF;
int i;
while(length--)
{ crc_value^=*data_value++;
for(i=0;i<8;i++)
{ if(crc_value&0x0001)
crc_value=( crc_value>>1)^0xA001;
else
crc_value= crc_value>>1;
}
}
return(crc_value);
}
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