TMP88CS38FG datasheet(97/226 Pages) TOSHIBA

97 / 226 page

TMP88CS38/CM38A/CP38A

2007-09-12

88CS38-97

2.9.8

Data Transfer of I

2C Bus

(1) Device initialization

For initialization of device, set the ACK in SBICRA to “1” and the BC to “000”.

Specify the data length to 8 bits to count clocks for an acknowledge signal. Set a

transfer frequency to the SCK in SBICRA.

Next, set the slave address to the SA in I2CAR and clear the ALS to “0” to set an

addressing format.

After confirming that the serial bus interface pin is high-level, for specifying the

default setting to a slave receiver mode, clear “0” to the MST, TRX and BB in SBICRB,

set “1” to the PIN, “10” to the SBIM, and “00” to bits SWRST1 and SWRST0.

Note:

The initialization of a serial bus interface circuit must be complete within the time

from all devices which are connected to a bus have initialized to and device does

not generate a start condition. If not, the data can not be received correctly because

the other device starts transferring before an end of the initialization of a serial bus

interface circuit.

(2) Start condition and slave address generation

Confirm a bus free status (when BB

= 0).

Set the ACK to “1” and specify a slave address and a direction bit to be transmitted to

the SBIDBR.

By writing “1” to the MST, TRX, BB and PIN, the start condition is generated on a

bus and then, the slave address and the direction bit which are set to the SBIDBR are

output. An INTSBI interrupt request occurs at the 9th falling edge of a SCL clock cycle,

and the PIN is cleared to “0”. The SCL pin is pulled down to the low level while the PIN

is “0”. When an interrupt request occurs the TRX changes by the hardware according

to the direction bits only when an acknowledge signal is returned from the slave device.

Note 1: Do not write a slave address to be output to the SBIDBR while data is transferred. If

data is written to the SBIDBR, data to been outputting may be destroyed.

Note 2: The bus free must be confirmed by software within 98.0

μs (the shortest

transmitting time according to the I

2C bus standard) after setting of the slave

address to be output. Only when the bus free is confirmed, set “1” to the MST, TRX,

BB, and PIN doesn’t finish within 98.0

μs, the other masters may start the

transferring and the slave address data written in SBIDBR may be broken.

Figure 2.9.13 Start Condition Generation and Slave Address Transfer

Acknowledge

signal from a

slave device

SCL pin

SDA pin

Start condition

Slave address

+ direction bit

345678

R/ W

INTSBI

interrupt

request

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