Goodrive270 series VFD for fan and pump Communication protocol
-299-
The calculation adopts the international standard CRC check rule. You can refer to the related
standard CRC algorithm to compile the CRC calculation program as required.
The following example is a simple CRC calculation function for your reference (using the C
programming language):
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 code 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, if the master reads two contiguous pieces of data (that is, to read content from the data
addresses 0004H and 0005H) from the VFD whose address is 01H, the frame structures are
described in the following.
RTU master command (from the master to the VFD)
To Next Page
Loading...
Need help?
General
