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 serial 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 controller 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 rising edge of the RD signal. The

clocked out data will appear on the data line. The host controller

can use the next falling 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 sig-

nal.

4

DATA

I/O Serial data input/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 se-

lected 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 Maxi-

mum 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 expo-

sure to extreme conditions may affect device reliability.

HT1623

5

April 21, 2000