Datasheet

V850ES/JG3 CHAPTER 25 CRC FUNCTION

R01UH0015EJ0300 Rev.3.00 Page 718 of 870

Sep 30, 2010

Communication errors can easily be detected if the CRC code is transmitted/received along with transmit/receive data

when transmitting/receiving data consisting of several bytes.

The following is an illustration using the transmission of 12345678H (0001 0010 0011 0100 0101 0110 0111 1000B)

LSB-first as an example.

Figure 25-4. CRC Transmission Example

Transmit/receive data

(12345678H)

CRC code

(08F6H)

56 34 12 F6 08

Setting procedure on transmitting side

<1> Write the initial value 0000H to the CRCD register.

<2> Write the 1 byte of data to be transmitted first to the transmit buffer register. (At this time, also write the same

data to the CRCIN register.)

<3> When transmitting several bytes of data, write the same data to the CRCIN register each time transmit data is

written to the transmit buffer register.

<4> After all the data has been transmitted, write the contents of the CRCD register (CRC code) to the transmit

buffer register and transmit them. (Since this is LSB first, transmit the data starting from the lower bytes, then

the higher bytes.)

Setting procedure on receiving side

<1> Write the initial value 0000H to the CRCD register.

<2> When reception of the first 1 byte of data is complete, write that receive data to the CRCIN register.

<3> If receiving several bytes of data, write the receive data to the CRCIN register upon every reception completion.

(In the case of normal reception, when all the receive data has been written to the CRCIN register, the

contents of the CRCD register on the receiving side and the contents of the CRCD register on the transmitting

side are the same.)

<4> Next, the CRC code is transmitted from the transmitting side, so write this data to the CRCIN register similarly

to receive data.

<5> When reception of all the data, including the CRC code, has been completed, reception was normal if the

contents of the CRCD register are 0000H. If the contents of the CRCD register are other than 0000H, this

indicates a communication error, so transmit a resend request to the transmitting side.