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2013-06-0002

PT0205-9

06/18/13

17

PT7C4337

Real-time Clock Module (I

Starting and Stopping I

Fig 2. Starting and stopping on I

1) START condition, repeated START condition, and STOP condition

a) START condition

SDA level changes from high to low while SCL is at high level

b) STOP condition

SDA level changes from low to high while SCL is at high level

c) Repeated START condition (RESTART condition)

In some cases, the START condition occurs between a previous START condition and the next STOP condition, in

which case the second START condition is distinguished as a RESTART condition. Since the required status is the same as for the

START condition, the SDA level changes from high to low while SCL is at high level.

2) Data Transfers and Acknowledge Responses during I

a)

Data transfers

Data transfers are performed in 8-bit (1 byte) units once the START condition has occurred. There is no limit on the amount

(bytes) of data that are transferred between the START condition and STOP condition.

The address auto increment function operates during both write and read operations.

Updating of data on the transmitter (transmitting side)'s SDA line is performed while the SCL line is at low level.

The receiver (receiving side) captures data while the SCL line is at high level.

*Note with caution that if the SDA data is changed while the SCL line is at high level, it will be treated as a START, RESTART,

or STOP condition.

b)

Data acknowledge response (ACK signal)

When transferring data, the receiver generates a confirmation response (ACK signal, low active) each time an 8-bit data segment

is received. If there is no ACK signal from the receiver, it indicates that normal communication has not been established. (This

does not include instances where the master device intentionally does not generate an ACK signal.)

Immediately after the falling edge of the clock pulse corresponding to the 8th bit of data on the SCL line, the transmitter releases

the SDA line and the receiver sets the SDA line to low (= acknowledge) level.