Inter-Integrated Circuit (I2C) Interface - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 571

Example 11.10
▼

Write a function to configure the DS1631A in Figure 11.34 to operate in continuous conver-
sion mode and set the T OUT polarity to active high. Assume that the I 2 C has only one master
and there is no possibility in getting bus collision.
Solution: The procedure for configuring the DS1631A is as follows:

Step 1
Assert a start condition and send a control byte (0x92) to the DS1631A with R/W 5 0.
Step 2
Wait until the I 2 C transfer is completed and check to see if the DS1631A acknowledges. If
not, exit.
Step 3
Send an Access-Config command to the DS1631A.
Step 4
Wait until the I 2 C bus is idle and check to see if the DS1631A acknowledges. If not, exit.
Step 5
Write a command byte to configure the DS1631A to operate in continuous conversion
mode and set the T OUT polarity to active high.
Step 6
Wait until the I 2 C bus is idle and check to see if the DS1631A acknowledges. If not, exit.

Step 7
Assert a stop condition to complete the whole process.

The assembly function that performs the desired confi guration is as follows:

openDS1631 ldaa #$92

jsr sendSlaveID

brclr IBSR,RXAK,openOK0 ; did DS1631A acknowledge?

ldab #$FF ; return error code 21

rts

openOK0 movb #$AC,IBDR ; send the Access Config command

brclr IBSR,IBIF,*

movb #IBIF,IBSR ; clear the IBIF flag

brclr IBSR,RXAK,openOK1 ; did DS1316A acknowledge?

ldab #$FF

rts

openOK1 stab IBDR ; sends configuration data

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

movb #IBIF,IBSR ; clear the IBIF flag

brclr IBSR,RXAK,openOK2 ; did DS1316A acknowledge?

ldab #$FF

rts

openOK2 bclr IBCR,MSSL ; generate a stop condition

ldab #0 ; normal return code

rts