Internal Memory Configuration and External Expansion - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 716

while(!(FSTAT&CCIF)); // wait for the last command to complete

return 0;

}

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Example 14.9
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Write a function that performs the erase-and-verify command to the flash memory. The
index register contains a word-aligned address to the flash block to be erased and verified.
Solution: The assembly routine that performs the erase-and-verify command is as follows:
feraseverify brclr FSTAT,CBEIF,cantE ; command buffer not empty

std 0,x ; write any data to flash sector address

movb #EraseVerify,FCMD ; write the command

movb #CBEIF,FSTAT ; launch the erase and verify command

brclr FSTAT,ACCERR+PVIOL,EVNoErr

ldab #1 ; return error code 1

rts

EVNoErr brclr FSTAT,CCIF,EVNoErr ; wait until command is done

brset FSTAT,BLANK,EVFOK ; successful erase and verify?

cantE ldab #1 ; flash is not blank

rts

EVFOK clrb ; erase and verify OK

rts
The C function that performs the erase-and-verify operation is as follows:
int feraseverify(int *ptr)
{

if(!(FSTAT & CBEIF))

return 1; // command buffer not empty, returns

*ptr 5 0x00; // write data to flash sector address

FCMD 5 EraseVerify; // write erase verify command

FSTAT 5 CBEIF; // launch the command

if(FSTAT&(ACCERR | PVIOL))

return 1; // errors have occurred

while(!(FSTAT & CCIF)); // wait until command is completed

if(FSTAT & BLANK)

return 0; // command completed successfully

else

return 1;

}

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14.6 The On-Chip EEPROM Memory

An HCS12 device may have 1, 2, or 4 kB of on-chip EEPROM to store nonvolatile data or
programs to be executed out of reset. The EEPROM is organized as an array of 2-byte words. For
example, the 4-kB EEPROM is organized as 2048 rows of 2 bytes (1 word). The EEPROM block's
erase sector size is two rows or two words.