Savch S3100A Series, Руководство пользователя

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Command code: 06H Write a word (Word)
For example: write 5000 (1388H) to the slave address 02H inverter 0003H address
Host command information Slave response information
ADR 02H ADR 02H
CMD 06H CMD 06H
Data address upper bit 00H Data address upper bit 00H
Data address lower bit 03H Data address lower bit 03H
Data content upper bit 13H Data content upper bit 13H
Data content lower bit 88H Data content lower bit 88H
CRC CHK lower bit
CRC CHK
CRC CHK lower bit
CRC CHK
CRC CHK upper bit CRC CHK upper bit
Checking method——CRC checking method:
In RTU frame format, the frame includes frame incorrect test field based on CRC computing. The CRC field
detects the content of whole frames. The CRC field is 2 bytes and includes 16-binary. It is added to frame after
being computed by transmission equipment. The receiving equipment recalculates the CRC which has received
frames and compare it with values in the received CRC field. If the two CRC values are different, it indicates that
there is transmission error received.
In CRC checking mode, it saves in 0xFFFF first, then uses a procedure and processes the continuous 8 more
than bytes in frames together with current register. Only the 8-bit data in every character is available to CRC, the
start bit, end bit and parity checking are all unavailable to it.
In CRC production course, every 8-bit character is different from the register content separately or (XOR). The
result moves to the direction of lowest effective bit. And the highest bit is filled with 0. LSB is picked up to test. If
LSB is 1, the register is different from the preset value alone. If LSB is 0, no actions.The whole process must be
repeated 8 times. As the last bit (8th bit) is finished, the next 8-bit character is different from the present value of
register again. The final value in register is the CRC value after all bytes in frame have been executed.
Here is a simple function of CRC algorithm for users' reference.
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);
}