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2015-08-0008

PT0508-1

08/24/15

7

PT7C4339/4339C

Real-time Clock Module

Functional Description

1. Overview of Functions

1.1. Clock function

CPU can read or write data including the year (last two digits), month, date, day, hour, minute, and second. Any (two-digit)

year that is a multiple of 4 is treated as a leap year and calculated automatically as such until the year 2100.

For PT7C4339 on a power-on reset (POR), the time and date are set to 00:00:00 01/01/00 (hh:mm:ss DD/MM/YY) and the

Day register is set to 01.

1.2. Alarm function

This device has two alarm system (Alarm 1 and Alarm 2) that outputs interrupt signals from SQW/INT to CPU when the

date, day of the week, hour, minute or second correspond to the setting. Each of them may output interrupt signal separately at a

specified time. The alarm is be selectable between on and off for matching alarm or repeating alarm.

1.3. Programmable square wave output

A square wave output enable bit controls square wave output at pin 7. Frequencies are selectable: 1, 4.096k, 8.192k, 32.768

kHz.

1.4. Interface with CPU

Data is read and written via the I2C bus interface using two signal lines: SCL (clock) and SDA (data).

Since the output of the I/O pin SDA is open drain, a pull-up resistor should be used on the circuit board if the CPU output I/O

is also open drain.

The SCL's maximum clock frequency is 400 kHz, which supports the I2C bus's high-speed mode.

1.5. Oscillator fail detect

When oscillator fail, PT7C4339 OSF bit will be set.

1.6. Oscillator enable/disable

Oscillator can be enabled or disabled at the same time by /EOSC bit.

2. Operation

The PT7C4339 operates as a slave device on the serial bus. Access is obtained by implementing a START condition and

providing a device identification code followed by data. Subsequent registers can be accessed sequentially until a STOP condition

3. Power Control

The power-control function is provided by a precise, temperature-compensated voltage reference and a comparator circuit

power to the device the time and date registers are reset to 01/01/00 01 00:00:00 (MM/DD/YY DOW HH:MM:SS).

Table 2:

Power Control Supply Condition

Read/Write Access

Power by

No

No

Yes

Yes