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Programmable Encoder IC
PT2241
FUNCTION DESCRIPTION
PT2241 encodes the address code (which are one-time programmable) and data into a special
waveform and outputs it to the DOUT. This waveform is fed to the RF modulator for transmission. The
transmitted radio frequency is received by the RF demodulator and reshaped into the special
waveform. PT2270 is then used to decode the waveform and set the corresponding output pin(s).
Thus, completing a remote control encoding and decoding function.
CODE BITS
A Code Bit is the basic component of the encoded waveform, and can be classified as either an
(Address/Data) Bit or a SYNC (Synchronous) Bit.
DATA BIT WAVEFORM
Data Bit can be designated as either Bit “0”, “1” or “f” if it is in “Low”, “High” or “Floating” State
respectively. One bit waveform consists of two pulse cycles and each pulse cycle has 128 oscillating
time periods. For further details, please refer to the diagram below:
α
OSC
B IT "0"
32
α
96
α
32
α
96
α
B IT "1"
96
α
32
α
96
α
32
α
B IT " f"
32
α
96
α
96
α
32
α
where: the oscillating time period,
α=1/f
and (f is the oscillation frequency)
As you can see in the diagram above, Bit “0” consists of 2 pulse cycles. Each Bit “0” pulse cycle goes
“High“ for 32α(where
α=
oscillating time period) then changes to “Low” for 96α. Likewise, Bit “1” has
2 pulse cycles and each Bit “1” pulse cycle consists of a “High” pulse for 96αis followed by “Low” Pulse
for 32α. For simplicity, let us designate one Bit “0” pulse cycle as a “Short Pulse” and one Bit “1” Pulse
Cycle as a “Long Pulse”. Then, we can say that a Bit “F” or a floating bit consists of a “Short Pulse”
followed by a “Long Pulse”.
PT2241 V1.5
-5-
March, 2006
PTC [ PRINCETON TECHNOLOGY CORP ]
