Intel® PXA255 Processor Developer’s Manual 9-21
I2C Bus Interface Unit
16. Write a 1 to the ISR[IRF] bit to clear the interrupt.
17. Read IDBR data.
18. Clear ICR[STOP] and ICR[ACKNAK] bits

9.6.5 Read 2 Bytes as a Master - Send STOP Using the Abort

1. L oad target slave address and R/nW bit in the IDBR. R/nW must be 1 for a read.
2. I nitiate the write.
Set ICR[START], clear ICR[STOP], clear ICR[ALDI E ], set ICR[TB]
3. When an IDBR Transmit Empty interrupt occurs.
Read ISR: IDBR Transmit Empty (1), Unit busy (1), R/nW bit (1)
4. Write a 1 to the ISR[ITE] bit to clear interrupt.
5. I nitiate the read
Clear ICR[START], clear ICR[STOP], set ICR[ALDIE], clear ICR[ACKNAK], set ICR[TB]
6. W hen an IDBR Receive full interrupt occurs.
Read ISR: IDBR Receive Full (1), Unit Busy (1), R/nW bit (1), ACK/NAK bit (0)
7. Write a 1 to the ISR[IRF] bit to clear the interrupt.
8. Read IDBR data.
9. Clear ICR[STOP] and ICR[ACKNAK] bits
10. Initiate the read.
Clear ICR[START], clear ICR[STOP], set ICR[ALDIE], set ICR[ACKNAK], set ICR[TB]
ICR[STOP] is not set because STOP or repeated start will be decided on the byte read.
11.Wh en an IDBR Receive full interrupt occurs.
Read ISR: IDBR Receive Full (1), Unit Busy (1), R/nW bit (1), ACK/NAK bit (1)
12. Write a 1 to the ISR[IRF] bit to clear the interrupt.
13. Read IDBR data.
14.Initiate STOP abort condition (STOP with no data transfer).
Set ICR[MA]
Note: If a NAK is not sent in Step 11, the next transaction must involve another data byte read.
9.7 Glitch Suppression Logic
The I2C unit has built-in glitch suppression logic that suppresses glitches of 60ns or less. This is
within the 50ns glitch suppression specification.
9.8 Reset Conditions
Software must ensure that the I2C unit is n ot busy before it asserts a reset. Software must also
ensure that the I2C bus is idle when the unit is enabled after reset. When directed to reset, the I2C
unit, except for ISAR, returns to the default reset condition. ISAR is not affected by a reset.