TMP86CS49FG datasheet(214/252 Pages) TOSHIBA

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16. Serial Bus Interface(I2C Bus) Ver.-D (SBI)

16.5 I2C Bus Control

TMP86CS49FG

In the master mode, a clock pulse for an acknowledge signal is not generated.

In the slave mode, a clock for a acknowledge signal is not counted.

16.5.2 Number of transfer bits

The BC (Bits7 to 5 in SBICRA) is used to select a number of bits for next transmitting and receiving data.

Since the BC is cleared to “000” by a start condition, a slave address and direction bit transmissions are

always executed in 8 bits. Other than these, the BC retains a specified value.

16.5.3 Serial clock

16.5.3.1 Clock source

The SCK (Bits2 to 0 in SBICRA) is used to select a maximum transfer frequency output from the SCL

pin in the master mode.

Four or more machine cycles are required for both high and low levels of pulse width in the external

clock which is input from SCL pin.

Note: Since the serial bus interface can not be used as the fast mode and the high-speed mode, do not set

SCK as the frequency that is over 100 kHz.

Figure 16-3 Clock Source

16.5.3.2 Clock synchronization

In the I2C bus, in order to drive a bus with a wired AND, a master device which pulls down a clock

pulse to low will, in the first place, invalidate a clock pulse of another master device which generates a

high-level clock pulse.

1/fscl

tLOW

tHIGH

tLOW = 2 /fc

tHIGH = 2 /fc + 8/fc

fscl = 1/(tLOW + tHIGH)

tSCKL tSCKH

tSCKL, tSCKH > 4 tcyc

Note 1: fc = High-frequency clock

Note 2: tcyc = 4/fc (in NORMAL mode, IDLE mode)

000

001

010

011

100

101

110

SCK (Bits2 to 0 in the SBICRA)

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