Inter-Integrated Circuit (I2C) Interface - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 575

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

if (IBSR & RXAK)

return 2 1;

IBDR 5 hibyte; /* send out the high byte of TH */

while(!(IBSR & IBIF));

IBSR 5 IBIF;

if (IBSR & RXAK)

return 2 1;

IBDR 5 lobyte; /* send out the low byte of TH */

while(!(IBSR & IBIF));

IBSR 5 IBIF;

if (IBSR & RXAK)

return 2 1;

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

return 0;

}

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Example 11.13
▼

Write a function to read the Config register from the DS1631A and return its value in ac-
cumulator B.
Solution: The procedure for reading the Config register is as follows:
Step 1
Assert the start condition and send the control byte 0x92 with R/W 5 0.
Step 2
Wait until the control byte is shifted out and check to see if the DS1631A acknowledges.
If not, exit.
Step 3
Send an Access Config command (0xAC) to the DS1631A.
Step 4
Wait until the command is shifted out and check to see if the DS1631A acknowledges.
If not, exit.
Step 5
Assert a restart condition.
Step 6
Send the control byte 0x93 with R/W 5 1, which tells the DS1631A that a read is being
performed.
Step 7
Wait until the control byte is shifted out and check to see if the DS1631A acknowledges.
If not, exit.
Step 8
Read the Config register.
Step 9
Make sure that the bus is idle and send back a NACK to the DS1631A.