Appendix A MODBUS Communication Protocol
Shenzhen Hpmont Technology Co., Ltd.
-76-
HD3Z Series User Manual V1.2
5.
Special Instruction
No. Special Instructions
1
For the data frame in ASCII mode, if the frame length is an even number, the frame is abandoned.
2
Host computer cannot restore to factory setting. It can read but not write these parameters:
F08 (Asyn motor parameter) and F17 (SCI parameter).
3
Host computer cannot modify F01.00 (User password). But it can write F01.00 to verify user password.
When verified, host computer access modifying function parameter of inverter. After modifying, write invalid
password into F01.00 to disable this access.
4
If many multi-function input terminals setting are the same, it may cause dysfunction. Therefore, the user
should avoid this case when modify the multi-function terminal function via the MODBUS.
6.
CRC Checking
Code of online calculating CRC 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));
}