M16C28 Datasheet, PDF (294/423 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/28 Group (M16C/28, M16C/28B)
16. MULTI-MASTER I²C bus INTERFACE
16.10 START Condition Duplicate Protect Function
A START condition is generated when verifying that the BB flag in the S10 register does not use buses.
However, if the BB flag is set to "1" (bus busy) by the START condition which other master device gener-
ates immediately after the BB flag is verified, the START condition is suspended by the START condition
duplicate protect function. When the START condition duplicate protect function starts, it operates as fol-
lows:
•Disable the start condition standby setting
If the function has already been set, first exit START condition standby mode and then set the MST and
TRX bits in the S10 register to "0".
•Writing to the S00 register is disabled. (The START condition trigger generation is disabled)
•If the START condition generation is interrupted, the AL flag in the S10 register becomes "1".(arbitration
lost detection)
The START condition duplicate protect function is valid between the SDA falling edge of the START condi-
tion and the receive completion of the slave address. Figure 16.15 shows the duration of the START
condition duplicate protect function.
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 duration of start condition duplicate protect
Figure 16.15 The duration of the start condition duplicate protect function
16.11 STOP Condition Generation Method
When the ES0 bit in the S1D0 register is set to “1” (I²C bus interface enabled) and the MST and TRX bits in
the S10 register are set to “1” at the same time, set the BB flag, PIN bit and 4 low-order bits in the S10
register to "0" simultaneously, to enter STOP condition standby mode. When dummy data is written to the
S00 register next, the STOP condition is generated. The STOP condition generation timing varies between
standard clock mode and high-speed clock mode. See Figure 16.17 and Table 16.8.
Until the BB flag in the S10 register becomes "0" (bus free) after an instruction to generate the STOP
condition is executed, do not write data to the S10 and S00 registers. Otherwise, the STOP condition
waveform may not be generated correctly.
If an input signal level of the SCL pin is set to low ("L") after the instruction to generate the STOP condition
is executed, a signal level of the SCL pin becomes high ("H"), and the BB flag is set to 0 (bus free), the MCU
outputs an "L" signal to SCL pin.
In that case, the MCU can stop an "L" signal output to the SCL pin by generating the STOP condition, writing
0 to the ES0 bit in the S1D0 register (disabled), or writing 1 to the IHR bit in the S1D0 register (reset
release).
Rev. 2.00 Jan. 31, 2007 ^{page 274} of 385
REJ09B0047-0200