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 HT1622

are disabled. The serial interface circuit is also reset. But if CS is

at logic low level and is input to the CS pad, the data and com-

mand transmission between the host controller and the HT1622

are all enabled.

2RD

I

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

the HT1622 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.

3WR

I

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

line are latched into the HT1622 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

If the system clock comes from an external clock source, the ex-

ternal clock source should be connected to the OSCI pad.

7

VDD

¾ Positive power supply

8

VLCD

I

LCD operating voltage input pad

9

IRQ

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

output

10, 11

BZ, BZ

O 2kHz or 4kHz tone frequency output pair

12~14

T1~T3

I

Not connected

15~22

COM0~COM7

O LCD common outputs

23~54

SEG0~SEG31

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 Absolute Maxi-

mum Ratings 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.

HT1622

5

April 21, 2000