C8051F980-C-GM Datasheet, PDF (173/325 Pages) Silicon Laboratories – Ultra Low Power, 8-2 kB Flash, Capacitive Sensing MCU

C8051F99x-C8051F98x
The 16-bit C8051F99x-C8051F98x CRC algorithm can be described by the following code:
unsigned short UpdateCRC (unsigned short CRC_acc, unsigned char CRC_input)
{
unsigned char i;
// loop counter
#define POLY 0x1021
// Create the CRC "dividend" for polynomial arithmetic (binary arithmetic
// with no carries)
CRC_acc = CRC_acc ^ (CRC_input << 8);
// "Divide" the poly into the dividend using CRC XOR subtraction
// CRC_acc holds the "remainder" of each divide
//
// Only complete this division for 8 bits since input is 1 byte
for (i = 0; i < 8; i++)
{
// Check if the MSB is set (if MSB is 1, then the POLY can "divide"
// into the "dividend")
if ((CRC_acc & 0x8000) == 0x8000)
{
// if so, shift the CRC value, and XOR "subtract" the poly
CRC_acc = CRC_acc << 1;
CRC_acc ^= POLY;
}
else
{
// if not, just shift the CRC value
CRC_acc = CRC_acc << 1;
}
}
// Return the final remainder (CRC value)
return CRC_acc;
}
Table 16.1 lists several input values and the associated outputs using the 16-bit C8051F99x-C8051F98x
CRC algorithm:
Table 16.1. Example 16-bit CRC Outputs
Input
0x63
0x8C
0x7D
0xAA, 0xBB, 0xCC
0x00, 0x00, 0xAA, 0xBB, 0xCC
Output
0xBD35
0xB1F4
0x4ECA
0x6CF6
0xB166
Rev. 1.2
173