Posted on May 17, 2011 at 11:35It would be nice if the compiler supported an instruction like:
wData = (*((huge unsigned int *)(dwAddress)));
The compiler doesn't support this so we've created a routine. Here it is. Obviously you would want to work on every address in a page before swapping to the next page when computing your CRC.
BYTE byReadAddress(DWORD dwAddress)
{
BYTE byReturn;
BYTE byPage;
BYTE byOldPage;
BYTE * pbyOffset;
// Disable Interrupts so only this routine uses the DPP while it is changed.
di();
SWITCH_TO_DPR_PAGE;
// Find the 16k page boundary
byPage = (BYTE)(dwAddress / 0x4000);
byOldPage = DPR0;
// Calculate 14bit (16k) offset
pbyOffset =(BYTE *)(dwAddress & 0x3FFF);
// set the page, Read the byte & restore the page
DPR0 = byPage;
byReturn = *pbyOffset;
DPR0 = byOldPage;
ei();
return byReturn;
}
