Delta DVP-ES2/EX2/SS2/SA2/SX2/SE manual Exception response

DVP - ES2/EX2/SS2/SA2/SX2/SE Operation Manual - Programming

{

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
Starting Address	04
	00
Number of Points	00
	10
CRC CHK Low	3C
CRC CHK High	F6
END	No data input ≥ 10 ms

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