ht658 Linx Technologies, Inc., ht658 Datasheet - Page 4

• Manufacturer Part Number: ht658
• Description: Holtek Ht658/s Data Sheet
• Manufacturer: Linx Technologies, Inc.

Holtek HT658/S Data Sheet
The HT658 decoder provides ten address and 8
data pins in a 24 pin SOP package. It is paired
with the HT640 encoder. The decoders receive
data transmitted by the encoders and interpret
the first 10 bits of the code period as address and
the last 8 bits as data. A signal on the DIN pin
then activates the oscillator, which in turns
decodes the incoming address and data. The
decoders will check the received address twice
continuously. If all the received address codes
match the contents of the decoder’s local
address, the 8 bits of data are decoded to acti-
vate the output pins, and the VT pin is set high to
indicate a valid transmission. That will last until
the address code is incorrect or no signal has
been received. The output of the VT pin is high
only when the transmission is valid. Otherwise it
is low always. The output type is momentary. The
data outputs follow the encoder during a valid
transmission and then reset.
Note: The oscillator is disabled in the standby
state and activated as long as a logic “high” sig-
nal is applied to the DIN pin. i.e., the DIN should
be kept “low” if there is no signal input.
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
B B L L O O C C K K D D I I A A G G R R A A M M
DIN
Sync. Detector
OSC2 OSC1
Buffer
Oscillator
Transmission Gate Circuit
Address
Comparator
Data Detector
Divider
Comparator
VDD
Data Shift
Register
VSS
No
No
No
Control Logic
Data to Output &
Previous Stored
Standby Mode
Buffer
Address Bits
Activate VT
Completed?
Data Error?
of Checking
Address or
Matched?
Store Data
Power On
Code In?
2 Times
Match
Data?
Yes
Yes
Yes
Yes
Yes
Data
VT
No
No
Ignore the Rest of
Disable VT &
This Word
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