Delta DVP-ES2 - Manual (Page 612)

D V P - E S 2 / E X 2 / S S 2 / S A2 / S X 2 / S E O p e r a t i o n M a n u a l - P r o g r a m m i n g
{
reg_crc ^= *data++;
for (j=0;j<8;j++)
{
If (reg_crc & 0x01) reg_crc=(reg_crc>>1) ^ 0Xa001; /* LSB(b0)=1 */
else reg_crc=reg_crc >>1;
}
}
return reg_crc; // the value that sent back to the CRC register finally
}
Exception response:
The PLC is expected to return a normal response after receiving command messages from the master
device. The following content depicts the conditions that either no response situation occurs or an error
response is replied to the master device.
1. The PLC did not receive a valid message due to a communication error; thus the PLC has no
response. In this case, condition of communication timeout has to be set up in the master device
2. The PLC receives a valid message without a communication error, but cannot accommodate it. In
this case, an exception response will return to the master device. In the exception response, the
most significant bit of the original command code is set to 1, and an exception code explaining
the condition that caused the exception is returned.
An example of exception response of command code 01H and exception 02H:
Sent message:
Field Name Example (Hex)
START No data input ≥ 10 ms
Slave Address 01
Command code 01
04
Starting Address
00
00
Number of Points
10
CRC CHK Low 3C
CRC CHK High F6
END No data input ≥ 10 ms
4 - 1 0