IPE300 series engineering VFD Communication protocol
-278-
unsigned int crc_cal_value(unsigned char*data_value,unsigned char
data_length)
{
int i;
unsigned int crc_value=0xffff;
while(data_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);
}
In the ladder logic, CKSM uses the table look-up method to calculate the CRC value according to the
content in the frame. The program of this method is simple, and the calculation is fast, but the ROM
space occupied is large. Use this program with caution in scenarios where there are space
occupation requirements on programs.
9.4 RTU command codes and communication data
9.4.1 Command code 03H, reading N words (continuously up to 16 words)
The command code 03H is used by the master to read data from the VFD. The count of data to be
read depends on the "data count" in the command. A maximum of 16 pieces of data can be read. The
addresses of the read parameters must be contiguous. Each piece of data occupies 2 bytes, that is,
one word. The command format is presented using the hexadecimal system (a number followed by
"H" indicates a hexadecimal value). One hexadecimal value occupies one byte.
The 03H command is used to read information including the parameters and running status of the
VFD.
For example, to read two contiguous data content pieces from 0004H from the VFD with the address
of 01H (that is, to read content from data addresses 0004H and 0005H), the frame structure is as
follows:
RTU master command (from the master to the VFD)
T1-T2-T3-T4 (time gap with a min. length of 3.5 bytes)
To Next Page
Loading...
Need help?
General