C8051F93X Datasheet, PDF(170/330 Page) Silicon Laboratories – Pipelined intstruction architecture executes 70 of instruction in 1 or 2 system clocks

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C8051F93X Datasheet, PDF (170/330 Pages) Silicon Laboratories – Pipelined intstruction architecture executes 70 of instruction in 1 or 2 system clocks

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C8051F93x-C8051F92x

Table 15.2. Example 32-bit CRC Outputs

Input

0x63

0xAA, 0xBB, 0xCC

0x00, 0x00, 0xAA, 0xBB, 0xCC

Output

0xF9462090

0x41B207B3

0x78D129BC

15.3. Preparing for a CRC Calculation

To prepare CRC0 for a CRC calculation, software should select the desired polynomial and set the initial

value of the result. Two polynomials are available: 0x1021 (16-bit) and 0x04C11DB7 (32-bit). The CRC0

result may be initialized to one of two values: 0x00000000 or 0xFFFFFFFF. The following steps can be

used to initialize CRC0.

1. Select a polynomial (Set CRC0SEL to 0 for 32-bit or 1 for 16-bit).

2. Select the initial result value (Set CRC0VAL to 0 for 0x00000000 or 1 for 0xFFFFFFFF).

3. Set the result to its initial value (Write 1 to CRC0INIT).

15.4. Performing a CRC Calculation

Once CRC0 is initialized, the input data stream is sequentially written to CRC0IN, one byte at a time. The

CRC0 result is automatically updated after each byte is written. The CRC engine may also be configured to

automatically perform a CRC on one or more Flash sectors. The following steps can be used to automati-

cally perform a CRC on Flash memory.

1. Prepare CRC0 for a CRC calculation as shown above.

2. Write the index of the starting page to CRC0AUTO.

3. Set the AUTOEN bit in CRC0AUTO.

4. Write the number of Flash sectors to perform in the CRC calculation to CRC0CNT. ï

Note: Each Flash sector is 1024 bytes.

5. Write any value to CRC0CN (or OR its contents with 0x00) to initiate the CRC calculation. The

CPU will not execute code any additional code until the CRC operation completes.ï

See the note in SFR Definition 15.1. CRC0CN: CRC0 Control for more information on

how to properly initiate a CRC calculation.

6. Clear the AUTOEN bit in CRC0AUTO.

7. Read the CRC result using the procedure below.

15.5. Accessing the CRC0 Result

The internal CRC0 result is 32-bits (CRC0SEL = 0b) or 16-bits (CRC0SEL = 1b). The CRC0PNT bits

select the byte that is targeted by read and write operations on CRC0DAT and increment after each read or

write. The calculation result will remain in the internal CR0 result register until it is set, overwritten, or addi-

tional data is written to CRC0IN.

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