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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-
trollercanusethenextfallingedgetolatchtheclockedoutdata.
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
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, the OSCI and OSCO pads can be left open.
32
OSCO
O
33
VDD
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 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-
mumRatings maycausesubstantialdamagetothedevice.Functionaloperationofthisdevice
at other conditions beyond those listed in the specification is not implied and prolonged expo-
sure to extreme conditions may affect device reliability.
HT1647
Rev. 1.00
6
June 1, 2001