M16CSLASH29 datasheet(303/499 Pages) RENESAS

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16. MULTI-MASTER I2C bus INTERFACE

page 279

16.11 STOP Condition Generation Method

When the ES0 bit in the S1D0 register is set to 1 (I2C bus interface enabled) and bits MST and TRX 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 condi-

tion is executed, do not write data to registers S10 and S00. 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).

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 generates

immediately after the BB flag is verified, the START condition is suspended by the START condition dupli-

cate protect function. When the START condition duplicate protect function starts, it operates as follows:

•Disable the start condition standby setting

If the function has already been set, first exit START condition standby mode and then set bits MST and

TRX 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. Figure16.15 shows the duration of the START

condition duplicate protect function.

Figure 16.15 The duration of the start condition duplicate protect function

1 clock

1 bit

SCL

SDA

BB flag

2 bit

3 bit

2 clock

3 clock

8 bit

ACK bit

The duration of start condition duplicate protect

8 clock

ACK clock

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