Pad Description

Pad No.

Pad Name

I/O

Description

23

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

HT1647 are disabled. The serial interface circuit is also reset.

But if the CS is at a logic low level and is input to the CS pad, the

data and command transmission between the host controller

and the HT1647 are all enabled.

24

RD

I

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

the HT1647 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.

25

WR

I

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

line are latched into the HT1647 on the rising edge of the WR

signal.

26~29

DB0~DB3

I/O Parallel data input/output with a pull-high resistor

30

VSS

¾ Negative power supply for logic circuit, ground

31

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.

32

OSCO

O

33

VDD

¾ Positive power supply for logic circuit

34

VLCD

I

Power supply for LCD driver circuit

35

IRQ

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

output.

36, 37

BZ, BZ

O 2kHz or 4kHz frequency output pair (tristate output buffer)

38~41

T1~T4

I

Not connected

42~57

COM0~COM15 O LCD common outputs

58~99,

1~22

SEG0~SEG63

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.

HT1647

6

April 21, 2000