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Chapter 13 Inter-Integrated Circuit (MC9S12XDP512) Block Description
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 611
13.4.1.8 Handshaking
The clock synchronization mechanism can be used as a handshake in data transfer. Slave devices may hold
the SCL low after completion of one byte transfer (9 bits). In such case, it halts the bus clock and forces
the master clock into wait states until the slave releases the SCL line.
13.4.1.9 Clock Stretching
The clock synchronization mechanism can be used by slaves to slow down the bit rate of a transfer. After
the master has driven SCL low the slave can drive SCL low for the required period and then release it.If
the slave SCL low period is greater than the master SCL low period then the resulting SCL bus signal low
period is stretched.
13.4.2 Operation in Run Mode
This is the basic mode of operation.
13.4.3 Operation in Wait Mode
IIC operation in wait mode can be configured. Depending on the state of internal bits, the IIC can operate
normally when the CPU is in wait mode or the IIC clock generation can be turned off and the IIC module
enters a power conservation state during wait mode. In the later case, any transmission or reception in
progress stops at wait mode entry.
13.4.4 Operation in Stop Mode
The IIC is inactive in stop mode for reduced power consumption. The STOP instruction does not affect IIC
register states.
13.5 Resets
The reset state of each individual bit is listed in Section 13.3, “Memory Map and Register Definition,”
which details the registers and their bit-fields.
13.6 Interrupts
MC9S12XDP512 uses only one interrupt vector.
Table 13-9. Interrupt Summary
Internally there are three types of interrupts in IIC. The interrupt service routine can determine the interrupt
type by reading the status register.
Interrupt Offset Vector Priority Source Description
IIC
Interrupt
— — — IBAL, TCF, IAAS
bits in IBSR
register
When either of IBAL, TCF or IAAS bits is set
may cause an interrupt based on arbitration
lost, transfer complete or address detect
conditions