Inter-Integrated Circuit (I2C) Interface - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 585

while(!(IBSR&IBIF));

IBSR 5 IBIF; /* clear the IBIF flag */

if (IBSR & RXAK) /* error if EEPROM does not respond */

return 2 1;

IBCR & 5 , MSSL; /* generate a stop condition */

return 0; /* normal write code */

}

▲

Example 11.17
▼

Write a function that performs a pagewrite operation. The control byte, the starting address
of the destination, and the pointer to the data in RAM to be written are passed to this function.
Solution: The following function writes a block of up to 16 bytes to the EEPROM. The block
of data to be output is pointed to by X. The EEPROM ID and starting address to be output are
passed in accumulators A and B, respectively. The number of bytes to be output is passed in Y.
The error code 21 will be returned if the EEPROM does not respond to its ID.
EEpageWrite jsr sendSlaveID ; generate start condition and send out slave ID

brclr IBSR,RXAK,pwriteok1 ; does the EEPROM acknowledge?

ldab #$FF ; return error code 2 1

rts

pwriteok1 stab IBDR ; send out the starting address to be written

brclr IBSR,IBIF,* ; wait until the byte is shifted out

movb #IBIF,IBSR ; clear the IBIF flag

brclr IBSR,RXAK,w_loop ; does the EEPROM acknowledge?

ldab #$FF ; return error code 2 1

rts

w_loop cpy #0

beq done_EEwrite ; byte count is 0, done

movb 1,x 1 ,IBDR ; send out 1 byte

brclr IBSR,IBIF,* ; wait until the byte is shifted out

movb #IBIF,IBSR ; clear the IBIF flag

brclr IBSR,RXAK,okNxt ; receive ACK?

ldab #$FF

rts

okNxt dey ; decrement byte count

bra w_loop

done_EEwrite

bclr IBCR,MSSL ; generate a stop condition

ldab #0 ; return error code 0

rts
The C function that performs the pagewrite operation is as follows:
char EEpageWrite(char ID, char addr, char ByteCnt, char *ptr)
{

SendSlaveID(ID); /* send out EEPROM ID */

if (IBSR & RXAK)

return 2 1; /* return 2 1 if EEPROM did not respond */