Goodrive350-19 series VFD for crane
Communication protocol
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significant bit (LSB) to the most significant bit (MSB), and 0 is placed in the MSB. Then, LSB is
detected. If LSB is 1, the XOR operation is performed on the current value in the register and the
preset value. If LSB is 0, no operation is performed. This process is repeated 8 times. After the last bit
(8
th
bit) is detected and processed, the XOR operation is performed on the next 8-bit byte and the
current content in the register. The final values in the register are the CRC values obtained after
operations are performed on all the bytes in the frame.
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^=*dat+;
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.
10.4 RTU command code and communication data
10.4.1 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
