As it turns out there are 2 CRC Hardware methods on the TM32H745I. The  HAL_CRC_Calculate() / HAL_CRC_Accumulate() method may be used to calculate the CRC anywhere in the memory map. A processor running at 120Mhz took about 31.5mS to CRC 1M bank of...

That's what it was. I went beyond the address space. All good now.

I get a hard fault if I supply a length over 0x7fff. uint32_t HAL_CRC_Calculate(CRC_HandleTypeDef *hcrc, uint32_t pBuffer[], uint32_t BufferLength);

volatile unsigned int *codePointer = (volatile unsigned int *)0x08000000;

Using the CRC_UserDefinedPolynomial example HAL_CRC_Calculate(&CrcHandle, (uint32_t *)&codePointer, 32700);