Inter-Integrated Circuit (I2C) Interface - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 582

11.8.6 Circuit Connection Between the I 2 C Master and the 24LC08B
The circuit connection of a 24LC08B and the HCS12 MCU is similar to that in Figure
11.34. The diagram of a system with one DS1631A and one 24LC08B and the HCS12 MCU is
shown in Figure 11.40.

5 V 5 V

HCS12

DS1631A 24LC08B

2.2 k 2.2 k

Ω Ω 5 V 5 V

V DD V DD

SDA SDA A0

SCL SCL WP

A0 A1

INT0 T OUT A2 SCL

A1

SDA

V SS

GND A2

SCL

SDA

Figure 11.40 ■ Circuit connection of the HCS12MCU, 24LC08B, and DA1631A

Example 11.15
▼ Write a function to read a byte from the 24LC08B. Pass the control byte and address in ac-
cumulators A and B to this subroutine. Return the data byte and error code in A and B, respec-
tively. This function should check the error that the EEPROM did not acknowledge (implies
that 24LC08B may have failed).
Solution: The following assembly subroutine implements the procedure for random read
described earlier:
EErandomRead

jsr sendSlaveID ; send out 24LC08B ID and block address

brclr IBSR,RXAK,ranRdok0 ; does EEPROM acknowledge?

ldab #$FF ; return 2 1, if EEPROM does not ackowledge

rts

ranRdok0 stab IBDR ; send out EEPROM memory address

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

movb #IBIF,IBSR ; clear IBIF flag

brclr IBSR,RXAK,ranRdok1 ; does EEPROM acknowledge?

ldab #$FF ; return 2 1, if EEPROM does not ackowledge

rts

ranRdok1 bset IBCR,RSTA ; gener ate restart condition

oraa #$01 ; set R/W bit for read

staa IBDR ; resend the device ID