Emerson EV3200 User Manual page 59

Request format:
Protocol data unit
Function parameter
Initial register address
Operation register quantity
Register bytes number
Register contents
Response format:
Protocol data unit
Function parameter
Register address
Operation register quantity
Example:
Request frame: initial address F1.01, change two function parameters, the change contents in the sequence from low to high,
as in the table below.
Function
Address
parameter
05 10
Response frame:
Address
0x05
In RTU mode, when changing multiple function parameters, the max number is 22. In ASCII mode, the max number is halved.
If the operation request fails, error code and exception code forming the protocol data unit will be replied. The error code is
(Parameter + 0x80). For the error code, refer to the above description.
Modbus error detection mechanism:
Check sum of ASCII mode: LRC check sum covers the information part from slave address to data, equal to the complement
the of sum of the check data characters. For example: The complement of (01H+06H+00H+03H+03H+0xE8H) is 0AH。
Check sum of RTU mode: CRC-16 check sum covers information from slave address to data. The calculation is shown below:
unsigned int crc_check (unsigned char *data, unsigned char length)
{
int i;
unsigned crc_result=0xffff;
while(length--)
{
crc_result^=*data++;
for(i=0;i<8;i++)
{
if(crc_result&0x01)
crc_result=(crc_result>>1)^0xa001;
else
crc_result=crc_result>>1;
}
}
return (crc_result=((crc_result&0xff)<<8)|(crc_result>>8));}
1
2
2
1
2*operation register quantity
1
2
2
Initial
Register quantity
address
01 01 00
Function parameter Register address
0x10 0x01
EV3200 Door Control Inverter User Manual
Appendix 2 Modbus Communication Protocol
Data length (bytes)
Data length (bytes)
Modification contents
Bytes
F1.01
02 04 00
Register quantity
0x01 0x00
Range
0x06
0x0000 ~ 0xFFFF
0x0000 ~ 0x016
2* operation register quantity
Depending on parameter range
Range
0x06
0x0000 ~ 0xFFFF
0x0000 ~ 0x016
Check sum
F1.02
64 02 58 68
Check sum
0x02 0x10
55
86
0x70