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2015-12-0001

PT0280-8

12/11/15

27

PT7C43390/43390C

Real-time Clock Module

10.3. How to confirm a setting value for a register and the result of correction

This RTC does not adjust the frequency of the crystal oscillation by using the function of clock correction. Therefore users cannot

confirm if it is corrected or not by measuring output 32.768 kHz. When the function of clock correction is being used, the cycle of

1 Hz clock pulse output from the INT pin changes once in 20 times or 60 times, as shown in below figure.

Confirmation of the clock correction

Measure a and b by using the frequency counter*1. Calculate the average frequency (Tave) based on the measurement results.

Calculate the error of the clock based on the average frequency (Tave). The following shows an example for confirmation.

Confirmation example: When B0 =0, 66h is set

Measurement results: a = 1.000080 Hz, b = 0.998493 Hz

Calculating the average frequency allows to confirm the result of correction.

*1. Use a high-accuracy frequency counter of 7 digits or more.

Caution Measure the oscillation frequency under the usage conditions.

11. Serial Interface

11.1. I

a. Start condition

A start condition is when the SDA line changes "H" to "L" when the SCL line is in "H", so that the access starts.

b. Stop condition

A stop condition is when the SDA line changes "L" to "H" when the SCL line is in "H", and the access stops, so that the

PT7C43390 gets standby.

Start / Stop Conditions

c. Data transfer and acknowledgment signal

Data transmission is performed for every 1-byte, after detecting a start condition. Transmit data while the SCL line is in "L", and

be careful of spec of tSU.DAT and tHD. DAT when changing the SDA line. If the SDA line changes while the SCL line is in "H",

the data will be recognized as start/stop condition in spite of data transmission. Note that by this case, the access will be

interrupted. During data transmission, every moment receiving 1-byte data, the devices which work for receiving data send an