C8051F709-GQR Silicon Labs, C8051F709-GQR Datasheet - Page 212

• Manufacturer Part Number: C8051F709-GQR
• Description: 8-bit Microcontrollers - MCU 8kB 32B EEPROM Cap Sense
• Manufacturer: Silicon Labs

Specifications of C8051F709-GQR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

C8051F70x/71x
29.1. 16-bit CRC Algorithm
The C8051F70x/71x CRC unit calculates the 16-bit CRC MSB-first, using a poly of 0x1021. The following
describes the 16-bit CRC algorithm performed by the hardware:
1. XOR the most-significant byte of the current CRC result with the input byte. If this is the first iteration of
2. If the MSB of the CRC result is set, left-shift the CRC result, and then XOR the CRC result with the
3. If the MSB of the CRC result is not set, left-shift the CRC result.
4. Repeat at Step 2 for the number of input bits (8).
For example, the 16-bit C8051F70x/71x CRC algorithm can be described by the following code:
unsigned short UpdateCRC (unsigned short CRC_acc, unsigned char CRC_input){
}
Table 29.1 lists example input values and the associated outputs using the 16-bit C8051F70x/71x CRC
algorithm (an initial value of 0xFFFF is used):
212
the CRC unit, the current CRC result will be the set initial value (0x0000 or 0xFFFF).
polynomial (0x1021).
unsigned char i;
#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++)
{
}
return CRC_acc; // Return the final remainder (CRC value)
// Check if the MSB is set (if MSB is 1, then the POLY can "divide"
// into the "dividend")
if ((CRC_acc & 0x8000) == 0x8000)
{
}
else
{
}
// if so, shift the CRC value, and XOR "subtract" the poly
CRC_acc = CRC_acc << 1;
CRC_acc ^= POLY;
// if not, just shift the CRC value
CRC_acc = CRC_acc << 1;
0x00, 0x00, 0xAA, 0xBB, 0xCC
0xAA, 0xBB, 0xCC
Table 29.1. Example 16-bit CRC Outputs
Input
0x63
// loop counter
Rev. 1.0
0xBD35
0x6CF6
0xB166
Output