ht640-s Linx Technologies, Inc., ht640-s Datasheet - Page 4

• Manufacturer Part Number: ht640-s
• Description: Holtek Ht640/s Data Sheet
• Manufacturer: Linx Technologies, Inc.

Holtek HT640/S Data Sheet
The HT640/S encoder begins a three-word transmission cycle
when the transmission enable line (TE) is pulled high. This cycle
will repeat itself as long as the TE line is held high. Once TE falls
low, the encoder output completes its final cycle and then stops as
shown in the Encoder/Decoder Timing diagram. When a transmis-
sion enable signal is applied, the encoder scans and transmits the
status of the 18 bits of address/data serially in the order A0 to A9,
D0 to D7.
The status of each address/data pin can be individually preset to
logic high, low, or floating. The floating state data input is interpret-
ed as logic low by the decoders since the decoder output only has
two states. The address pins are usually set to transmit particular
security codes by DIP switches or PCB wiring, while the data is
selected using push buttons or electronic switches. The floating
state allows the HT640/S to be used without pull-up or pull-down
resistors on the data and address input lines.
F F U U N N C C T T I I O O N N A A L L D D E E S S C C R R I I P P T T I I O O N N
D D A A T T A A S S T T R R U U C C T T U U R R E E
B B L L O O C C K K D D I I A A G G R R A A M M
Pilot Period
(6 bits)
TE
A0
A9
1/6 bit
Sync. Period
OSC2
D0
Transmission
Gate Circuit
Oscillator
18
OSC1
D7
+18 Counter
+33 Divider
& 1 of 18
Decoder
Detector
Trinary
Address Code Period
Data Select
Circuit
Sync.
& Buffer
VDD
VSS
DOUT
No
Standby Mode
Data Code Period
3 Data Words
Still Enabled?
3 Data Words
Transmission
Transmission
Continuously
Transmitted
Transmitted
Power On
Enabled?
Yes
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