AN206373
F2MC/FR Family, All series, Method of confirming data in serial Communications
When MCU transmit/receive the data by the serial communications interface, there is a possibility of receiving wrong
data by the noise. Therefore, this application note explains the method of confirming data by using the checksum.
About the serial communications interface specification, please confirm the hardware manual of each MCU..
Contents
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2
1
Introduction ..................................................................1
Method of using checksum in serial communications ..2
Document History.............................................................. 3
Introduction
When MCU transmit/receive the data by the serial communications interface, there is a possibility of receiving wrong
data by the noise. Therefore, this application note explains the method of confirming data by using the checksum.
About the serial communications interface specification, please confirm the hardware manual of each MCU.
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Document No. 002-06373 Rev. *A
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F2MC/FR Family, All series, Method of confirming data in serial Communications
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Method of using checksum in serial communications
This chapter shows the method of calculating checksum by putting the 16 bit length data on some address. The
example of C language program to calculate checksum is shown as follows.
unsigned short calc_checksum( unsigned short *addr, int size)
{
unsigned long sum;
unsigned long checksum;
sum = 0;
while( size > 1 ){
sum+= *(addr++);
size-= 2;
}
if( size > 0 ){
sum+= (*addr) & 0xff00;
/* If byte data remains at the end, it is added */
}
sum = (sum & 0xffff) + (sum >> 16); /* To 16 bit length. */
checksum = ~sum;
/* Complement of one */
}
The transmitted side calculates checksum by the above-mentioned and adds it at the end of the transmission data.
The received side calculates by all receive data including checksum.
There is no error if the result of the calculation on the received side is 0xFFFF.
The mistake of the transmitting/receiving data can be easily confirmed by such a method.
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Document No. 002-06373 Rev.*A
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F2MC/FR Family, All series, Method of confirming data in serial Communications
Document History
2
Document Title: AN206373 - F MC/FR Family, All series, Method of confirming data in serial Communications
Document Number: 002-06373
Revision
ECN
Orig. of
Change
Submission
Date
**
-
YUIS
08/05/2008
First Edition
*A
5293564
YUIS
06/02/2016
Migrated Spansion Application Note “AN07-00155-1E” to Cypress format.
www.cypress.com
Description of Change
Document No. 002-06373 Rev.*A
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F2MC/FR Family, All series, Method of confirming data in serial Communications
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