Inter-Integrated Circuit (IIC)
MCF51CN128 Reference Manual, Rev. 6
17-24
Freescale Semiconductor
NOTE
In Master receive mode the FACK should be set zero before the last byte
transfer.
17.6.1
Byte Transfer Interrupt
The TCF (transfer complete flag) bit is set at the falling edge of the ninth clock to indicate the completion
of byte transfer.
17.6.2
Address Detect Interrupt
When the calling address matches the programmed slave address (IIC address register) or when the
GCAEN bit is set and a general call is received, the IAAS bit in the status register is set. The CPU is
interrupted, provided the IICIE is set. The CPU must check the SRW bit and set its Tx mode accordingly.
17.6.3
Arbitration Lost Interrupt
The IIC is a true multi-master bus that allows more than one master to be connected on it. If two or more
masters try to control the bus at the same time, the relative priority of the contending masters is determined
by a data arbitration procedure. The IIC module asserts this interrupt when it loses the data arbitration
process and the ARBL bit in the status register is set.
Arbitration is lost in the following circumstances:
•
SDA sampled as a low when the master drives a high during an address or data transmit cycle.
•
SDA sampled as a low when the master drives a high during the acknowledge bit of a data receive
cycle.
•
A START cycle is attempted when the bus is busy.
•
A repeated START cycle is requested in slave mode.
•
A STOP condition is detected when the master did not request it.
This bit must be cleared by software by writing a 1 to it.
17.6.4
Timeouts Interrupt in SMbus
When IICIE is set, the IIC asserts a timeout interrupt output SLTF upon detection of any of the mentioned
timeout conditions, with one exception. The HIGH TIMEOUT mechanism shall not be used to influence
the timeout interrupt output, because the HIGH TIMEOUT indicates an idle condition on the bus. SLTF
rises when it matches the HIGH TIMEOUT and fall automatically to just indicate the bus status.
Table 17-13. Interrupt Summary
Interrupt Source
Status
Flag
Local Enable
Complete 1-byte transfer
TCF
IICIF
IICIE
Match of received calling address
IAAS
IICIF
IICIE
Arbitration Lost
ARBL
IICIF
IICIE
SMBus Timeout Interrupt Flag
SLTF
IICIF
IICIE
