M16C6K9 Datasheet, PDF (200/292 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6K9 Group
MULTI-MASTER I²C-BUS Interface
Function of protection of duplicate START condition
It is necessary to verify that the bus is not in use via BB flag before setting up a START condition. However,
there is a possibility that right after the verification of BB flag, the BB flag becomes to “1” because a START
condition is generated by another master device .In this case, the function to interrupt the start condition is
built in. When the function starts, it works as follows:
•The prohibition of setting up START condition standby
If the START condition standby has been set up, releases it and resets the bits of MST and TRX.
•The prohibition of writing to the I²C data shift register (The prohibition of generating a START condition
trigger)
•If the generation of start condition is interrupted, sets the AL flag.
The function of protection of duplicate START condition is valid from the falling edge of SDA of START
condition to the completion of slave reception. Fig.GC-16 shows the valid period of the function of protection
of duplicate START condition.
SCL
SDA
BB flag
1 clock
1 bit
2 clock
2 bit
3 clock
3 bit
8 clock
8 bit
ACK clock
ACK bit
The valid period of protection of duplicate START condition
Fig.GC-16 The valid period of the function of protection of duplicate START condition
Rev.1.00 Jun 06, 2003 page 200 of 290