SI1002 参数 Datasheet PDF下载

Si1000/1/2/3/4/5

15.2. 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).

15.3. 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.



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.

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.

15.4. 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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