Block Diagram

Pin Assignment

Rev. 1.10

1

July 18, 2008

Features

· Operating voltage: 2.0V~5.5V

· Maximum input serial clock: 500kHz at VDD=2V,

2MHz at VDD=5V

· Operating current: less than 1mAat2V,

less than 1.2

mAat5V

· TTL compatible

- VIH: 2.0V~VDD+0.3V at VDD=5V

- VIL: -0.3V~+0.8V at VDD=5V

· Two data transmission modes: single-byte,

or burst mode

· Serial I/O transmission

· All registers store BCD format

· HT1380: 8-pin DIP package

HT1381: 8-pin SOP package

General Description

The HT1380/HT1381 is a serial timekeeper IC which

provides seconds, minutes, hours, day, date, month and

year information. The number of days in each month

and leap years are automatically adjusted. The

HT1380/HT1381 is designed for low power consump-

tion and can operate in two modes: one is the 12-hour

mode with an AM/PM indicator, the other is the 24-hour

mode.

The HT1380/HT1381 has several registers to store the

corresponding information with 8-bit data format. A

32768Hz crystal is required to provide the correct tim-

ing. In order to minimize the pin number, the

HT1380/HT1381 use a serial I/O transmission method

to interface with a microprocessor. Only three wires are

required: (1) REST, (2) SCLK and (3) I/O. Data can be

delivered 1 byte at a time or in a burst of up to 8 bytes.

Applications

· Microcomputer serial clock

· Clock and Calendar

1

2

3

4

8

7

6

5

N C

X 1

X 2

V S S

V D D

S C L K

I / O

R E S T

H T 1 3 8 0

8 D I P - A

1

2

3

4

8

7

6

5

N C

X 1

X 2

V S S

V D D

S C L K

I / O

R E S T

H T 1 3 8 1

8 S O P - A

R E S T

C o m m a n d

C o n t r o l L o g i c

X 1

X 2

S C L K

I / O

D a t a S h i f t

R e g i s t e r

R e a l T i m e

C l o c k

O s c i l l a t o r a n d

D i v i d e r C i r c u i t

HT1380