Symbol

Parameter

Test Conditions

Min.

Typ.

Max.

Unit

VDD

Conditions

tr

Clock Rise and Fall

Time

2V

¾¾

2000

ns

tf

5V

¾¾

500

tCC

Reset to Clock Setup

2V

¾

4

¾

us

5V

¾

1

¾

tCCH

Clock to Reset Hold

2V

¾

240

¾

ns

5V

¾

60

¾

tCWH

Reset Inactive Time

2V

¾

4

¾

us

5V

¾

1

¾

tCDZ

Reset to I/O High Im-

pedance

2V

¾¾

280

ns

5V

¾¾

70

Rev. 1.10

4

July 18, 2008

Functional Description

The HT1380/HT1381 mainly contains the following in-

ternal elements: a data shift register array to store the

clock/calendar data, command control logic, oscillator

circuit and read timer clock. The clock is contained in

eight read/write registers as shown below. Data con-

tained in the clock register is in binary coded decimal

format.

Two modes are available for transferring the data be-

tween the microprocessor and the HT1380/HT1381.

One is in single-byte mode and the other is in multi-

ple-byte mode.

The HT1380/HT1381 also contains two additional bits,

the clock halt bit (CH) and the write protect bit (WP).

These bits control the operation of the oscillator and so

data can be written to the register array. These two bits

should first be specified in order to read from and write

to the register array properly.

Command Byte

For each data transfer, a Command Byte is initiated to

specify which register is accessed. This is to determine

whether a read, write, or test cycle is operated and

whether a single byte or burst mode transfer is to occur.

Refer to the table shown below and follow the steps to

write the data to the chip. First give a Command Byte of

HT1380/HT1381, and then write a data in the register.

This table illustrates the correlation between Command Byte and their bits:

Function Description

Command Byte

C7

C6

C5

C4

C3

C2

C1

C0

Select Read or Write Cycle

R/W

Specify the Register to be Accessed

A2

A1

A0

Clock Halt Flag

C

For IC Test Only

1001

x

x

x

1

Select Single Byte or Burst Mode

1011111

x

Note:

²x² stands for don¢t care