
Rev. 1.0, 02/00, page 502 of 1141
23.3.7
Automatic Switching from Formatless Transfer to I
2
C Bus Format Transfer
Setting the SW bit in DDCSWR to 1 selects the IIC0 formatless transfer operation. When an SCL
falling edge is detected, the operating mode automatically switches from formatless transfer to I
2
C
bus format transfer (slave mode). For automatic switching to be possible, the following four
conditions must be observed:
1. The same data pin (SDA) is used in common for formatless transfer and I
2
C bus format
transfer.
2. Separate clock pins are used for formatless transfer and I
2
C bus format transfer (SYNC1 for
formatless, and SCL for I
2
C bus format)
3. The SCL pin is kept high during formatless transfer.
4. Register bits other than the TRS bit in ICCR are set to appropriate values so that I
2
C bus
format transfer can be performed.
The operating mode is automatically switched from formatless transfer to I
2
C bus format transfer
when an SCL falling edge is detected and the SW bit in DDCSWR is automatically cleared to 0.
To switch the mode from I
2
C bus format transfer to formatless transfer, set the SW bit to 1 by
software.
During formatless transfer, do not modify the bits that control the I
2
C bus interface operating
mode, such as the MSL or TRS bit. When switching from the I
2
C bus format transfer to formatless
transfer, specify the formatless transfer direction (transmit or receive) by setting or clearing the
TRS bit, then set the SW bit to 1. After the automatic switching from formatless transfer to I
2
C bus
format transfer (slave mode), the TRS bit is automatically cleared to 0 to enter the slave address
receive wait state.
If an SCL falling edge is detected during formatless transfer, the IIC does not wait for the stop
condition but switches the operating mode immediately.