Pad Description

Pad No.

Pad Name

I/O

Description

1

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.

2

OSCO

O

3

VDD

¾ Positive power supply

4

VLCD

I

LCD operating voltage input pad.

5

IRQ

O Time base or Watchdog Timer overflow flag, NMOS open drain

output

6, 7

BZ, BZ

O 2kHz or 4kHz tone frequency output pair

8~11

T1~T4

I

Not connected

12~27

COM0~COM15

O LCD common outputs

28~75

SEG0~SEG47

O LCD segment outputs

76

CS

I

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

logic high, the data and command read from or write to the

HT1626 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 HT1626 are all enabled.

77

RD

I

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

the HT1626 are clocked out on the rising edge of the RD signal.

The clocked out data will appear on the data line. The host con-

troller can use the next falling edge to latch the clocked out data.

78

WR

I

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

line are latched into the HT1626 on the rising edge of the WR

signal.

79

DATA

I/O Serial data input/output with pull-high resistor

80

VSS

¾ Negative power supply, Ground

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 de-

vice at other conditions beyond those listed in the specification is not implied and prolonged

exposure to extreme conditions may affect device reliability.

HT1626

5

April 21, 2000