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Function Description

PT0205(02/07)

Ver: 1

5

Data Sheet

PT7C4337

Real-time Clock Module (I

2

C Bus)

Overview of Functions

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.

Alarm function

This device has two alarm system (Alarm 1 and Alarm 2) that outputs interrupt signals from INTA or INTB 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.

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, 32.768k Hz.

Interface with CPU

Data is read and written via the I

2

C 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 I

2

C bus's high-speed mode.

Oscillator fail detect

When oscillator fail, PT7C4337 OSF bit will be set.

Oscillator enable/disable

Oscillator and time count chain can be enabled or disabled at the same time by /ETIME bit.