Pad Description

Pad No.

Pad Name

I/O

Description

1CS

I

Chip selection input with pull-high resistor. When the CS is logic high, the

data and command read from or written to the HT1623 are disabled. The se-

rial interface circuit is also reset But if the CS is at logic low level and is input

to the CS pad, the data and command transmission between the host con-

troller and the HT1623 are all enabled.

2RD

I

READ clock input with pull-high resistor. Data in the RAM of the HT1623 are

clocked out on the falling edge of the RD signal. The clocked out data will ap-

pear on the data line. The host controller can use the next rising edge to latch

the clocked out data.

3WR

I

WRITE clock input with pull-high resistor. Data on the DATA line are latched

into the HT1623 on the rising edge of the WR signal.

4

DATA

I/O

Serial data input or output with pull-high resistor

5

VSS

¾

Negative power supply, ground

6

OSCI

I

The OSCI and OSCO pads are connected to a 32.768kHz crystal in order to

generate a system clock. If the system clock comes from an external clock

source, the external clock source should be connected to the OSCI pad. But

if an on-chip RC oscillator is selected instead, the OSCI and OSCO pads can

be left open.

7

OSCO

O

8

VDD

¾

Positive power supply

9

VLCD

I

LCD operating voltage input pad.

10

IRQ

O

Time base or watchdog timer overflow flag, NMOS open drain output

11, 12

BZ, BZ

O

2kHz or 4kHz tone frequency output pair

13~15

T1~T3

I

Not connected

16~23

COM0~COM7

O

LCD common outputs

24~71

SEG0~SEG47

O

LCD segment outputs

Absolute Maximum Ratings

Supply Voltage .........................................

-0.3V to 5.5V

Storage Temperature ............................

-50°Cto125°C

Operating Temperature...........................

-25°Cto75°C

Note: These are stress ratings only. Stresses exceeding the range specified under

²Absolute Maximum Ratings² may

cause substantial damage to the device. Functional operation of this device at other conditions beyond those

listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliabil-

ity.

HT1623

Rev. 1.10

5

September 11, 2002