
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
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-
trollercanusethenextfallingedgetolatchtheclockedoutdata.
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
Negative power supply, Ground
Absolute Maximum Ratings
Supply Voltage.............................. 0.3V to 5.5V
Storage Temperature................. 50 C to 125 C
Input Voltage................V
SS
0.3V to V
DD
+0.3V
Operating Temperature .............. 25 C to 75 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.
HT1626
5
April 21, 2000