Internal Memory Configuration and External Expansion - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 723

Example 14.11
▼

Write a function that performs bulk erasure to the EEPROM. Index register X contains a
word-aligned EEPROM address.
Solution: The assembly function that performs EEPROM bulk erasure is as follows:
bulkeraseEE movb

#ACCERR 1 PVIOL,ESTAT ; clear error flags

brclr ESTAT,CBEIF,EEBEErr ; command buffer not empty, return

std 0,X ; write any data to EEPROM

movb #BulkErase,ECMD ; write bulk-erase command

movb #CBEIF,ESTAT ; launch bulk-erase command

brclr ESTAT,ACCERR 1 PVIOL,EEBROK ; check error ; no error?

EEBEErr ldab #1 ; error code set to 1

rts

EEBROK brclr ESTAT,CCIF,EEBROK ; wait until command completion

clrb

rts

▲
The C language version of the function is straightforward and hence is left as an exercise.

Example 14.12
▼

Write a function that bulk-erases the EEPROM and verifies if the whole EEPROM is blank.
The index register X contains a valid word-aligned address to the EEPROM.
Solution: The assembly function that performs the specified operation is as follows:
eeraseverify movb

#ACCERR 1 PVIOL,ESTAT ; clear error flags

brclr ESTAT,CBEIF,cantEE ; command buffer not empty

std 0,x ; write any data to EEPROM address

movb #EraseVerify,ECMD ; write the command

movb #CBEIF,ESTAT ; launch the erase and check command

brclr ESTAT,ACCERR 1 PVIOL,EEEVOK

ldab #1 ; return error code 1

rts

EEEVOK brclr ESTAT,CCIF,EEEVOK ; wait until command is done

brset ESTAT,BLANK,EVEOK ; successful erase and verify?

cantEE ldab #1 ; EEPROM is not blank

rts

EVEOK clrb

rts

▲

The C language version of the function is straightforward and is left as an exercise.

Example 14.13
▼ Write a function that programs a word to the EEPROM. X contains the address of
the EEPROM location to be programmed, and double accumulator D holds the data to be