AM263P4-Q1: About Memory Cyclic Redundancy Check (MCRC)

Imaoka,

Before diving into the implementation details, I want to flag an important clarification about your parameters. The value 0xEDB88320 is the reflected polynomial for CRC-32 (IEEE 802.3), not a seed/initial value. The standard CRC-32 initial value is 0xFFFFFFFF (which you also list separately). The MCRC hardware uses a fixed polynomial selected by the CRC type setting — you don't configure the polynomial via the seed register. I'll address your questions assuming you want standard IEEE 802.3 CRC-32 behavior.

What the SDK Supports via APIs

The SDL_MCRC_Config_t structure and associated APIs give you control over several parameters in both Semi-CPU and Auto modes [1][2]:

typedef struct SDL_MCRC_Config_s
{
    SDL_MCRC_Type_t      type;        // CRC type selection
    SDL_MCRC_DataLength_t dataLen;    // Data width
    SDL_MCRC_DataBitSize  dataBitSize;// Input data size (8, 16, 32, 64-bit)
    SDL_MCRC_BitSwap_t    bitSwap;   // Bit ordering (MSB/LSB)
    SDL_MCRC_ByteSwap_t   byteSwap;  // Byte swap enable/disable
} SDL_MCRC_Config_t;

1. Data Size Unit (8-bit / byte-by-byte) —  Supported

Set dataBitSize to SDL_MCRC_DATA_8_BIT in the configuration structure [3]:

SDL_MCRC_Config_t mcrcConfig = {
    .type        = SDL_MCRC_TYPE_32BIT,
    .dataLen     = SDL_MCRC_DATALENGTH_32BIT,
    .dataBitSize = SDL_MCRC_DATA_8_BIT,    // byte-by-byte processing
    .bitSwap     = SDL_MCRC_BITSWAP_MSB,
    .byteSwap    = SDL_MCRC_BYTESWAP_ENABLE
};
SDL_MCRC_addConfig(instance, channel, &mcrcConfig);

Important caveat: Although you can specify 8-bit data patterns, the data written to the PSA register is always 64 bits wide internally — patterns smaller than 64 bits are zero-padded [4]. This means the resulting signature will differ from a pure software CRC-32 byte-by-byte calculation. You will need to verify that the output matches your expected IEEE 802.3 results with your specific data.

2. Initial Value (0xFFFFFFFF) —  Supported via Seed

Use SDL_MCRC_setPSASeedSig() to set the initial value [5]:

SDL_MCRC_Signature_t seedValue;
seedValue.regL = 0xFFFFFFFFU;  // Lower 32 bits
seedValue.regH = 0xFFFFFFFFU;  // Upper 32 bits (64-bit PSA register)

SDL_MCRC_setPSASeedSig(instance, channel, &seedValue);

This sets the PSA register's starting state before CRC computation begins.

3. Final XOR Inversion (XOR with 0xFFFFFFFF) —  Not Supported in Hardware

The MCRC hardware does not natively support final XOR inversion of the output signature [6]. You must perform this step in software after retrieving the computed signature:

SDL_MCRC_Signature_t resultSig;
SDL_MCRC_getPSASectorSig(instance, channel, &resultSig);

// Apply final XOR inversion in software
uint32_t finalCRC = resultSig.regL ^ 0xFFFFFFFFU;

In Semi-CPU mode, you read the signature from the PSA Sector Signature Registers and apply the XOR yourself [7]. In Auto mode, the hardware compares the signature against a pre-stored reference value — so you would need to store the pre-inverted expected CRC in the CRC Value Register to account for the missing final XOR step [7].

Recommended Programming Sequence

For Semi-CPU mode [8]:

1. SDL_MCRC_channelReset(instance, channel)
2. SDL_MCRC_init(instance, channel, watchdogPreload, blockPreload)
3. SDL_MCRC_config(instance, channel, patternCount, sectorCount, SDL_MCRC_OPERATION_MODE_SEMICPU)
4. SDL_MCRC_addConfig(instance, channel, &mcrcConfig)
5. SDL_MCRC_setPSASeedSig(instance, channel, &seedValue)
6. Transfer data via DMA to PSA signature register
7. SDL_MCRC_getPSASectorSig(instance, channel, &resultSig)
8. Apply resultSig.regL ^= 0xFFFFFFFF in software

Open Items to Verify

• Bit/byte swap settings: Achieving IEEE 802.3-compliant output may require specific combinations of bitSwap and byteSwap. The standard CRC-32 involves bit-reversal of input bytes, which the SDL_MCRC_BITSWAP_LSB setting may address — but this needs empirical verification against known test vectors.
• 64-bit zero-padding impact: Since 8-bit data is padded to 64 bits internally, confirm the computed signature matches your reference implementation with a known data set before relying on it in production.

I'd recommend running a simple test with a known input (e.g., the ASCII string "123456789" which should yield CRC-32 = 0xCBF43926) to validate your configuration.

1. SDL MCRC Header Source
2. SDL MCRC API Guide
3. SDL MCRC Header - DataBitSize Enum
4. SDL MCRC API - PSA Register Padding
5. SDL MCRC API - setPSASeedSig
6. AM263PX TRM - MCRC Module
7. AM263PX TRM - Semi-CPU and Auto Mode
8. SDL MCRC Example Page

Best Regards,

Zackary Fleenor