HCS473 Datasheet, PDF (16/68 Pages) Microchip Technology – Code Hopping Encoder and Transponder

HCS473
3.1.4 ENCODER MODE OPTIONS
The following HCS473 configuration options configure
transmission characteristics of the information exiting
the DATA pin:
• Modulation select (MSEL)
• Header select (HSEL)
• Extended serial number (XSER)
• Queue counter enable (QUEN)
• Counter select (CNTSEL)
• Low voltage trip point (VLOWSEL)
• PLL interface select (AFSK)
• RF enable output (RFEN)
• Seed button code (SDBT)
• Time before Seed (SDTM)
• Limited Seed (SDLM)
• Seed mode (SDMD)
• RF baud rate select (RFBSL)
• Guard time select (GSEL)
• Minimum code words (MTX)
• Timeout select (TSEL)
• Long preamble enable (LPRE)
• Long preamble length (LPRL)
• Preamble duty cycle (PRD)
The following sections detail each configuration’s avail-
able options. All timing values specified are subject to
the specified oscillator variation.
3.1.4.1 Modulation Format (MSEL)
The Modulation format option selects the modulation
format for data output from the DATA pin; most often
transmitted via RF.
MSEL options:
• Pulse Width Modulation (PWM), Figure 3-3
• Manchester Modulation, Figure 3-4
3.1.4.2 Header Select (HSEL)
The synchronization header is typically used by the
receiver to adjust bit sampling appropriate to the trans-
mitter’s current speed; as the transmitter’s RC oscilla-
tor varies with temperature and voltage, so will the
transmission’s timing.
HSEL options:
• 4 RFTE
• 10 RFTE
3.1.4.3 Extended Serial Number (XSER)
The Extended Serial Number option determines
whether the HCS473 transmits a 28 or 32-bit serial
number.
When configured for a 28-bit serial number, the Most
Significant nibble of the 32 bits reserved for the serial
number is replaced with a copy of the 4-bit button sta-
tus, Figure 3-2.
XSER options:
• 28-bit serial number
• 32-bit serial number
3.1.4.4 Queue Counter (QUEN)
The QUE counter can be used to request secondary
decoder functions using only a single transmitter but-
ton. Typically a decoder must keep track of incoming
transmissions to determine when a double button press
occurs, perhaps an unlock all doors request. The QUE
counter removes this burden from the decoder by
counting multiple button presses and including the
QUE counter value in the last two bits of the 69-bit code
word, (Figure 3-2). If QUEN is disabled, the transmis-
sion will consist only of 67 bits as the QUE bits field is
not transmitted.
Que counter functionality is enabled with the QUEN
configuration option. The 2-bit QUE counter is incre-
mented each time an active button input is released for
at least the Debounce Time (TDB), then re-activated
(button pressed again) within the Queue Time (TQUE),
Figure 3-5. The counter increments up from 0 to a max-
imum of 3, returning to 0 only after a different button
activation or after button activations spaced greater
than the Queue Time (TQUE) apart.
The current transmission aborts, after completing the
minimum number of code words (Section 3.1.4.15),
when the active button inputs are released. A button re-
activation within the queue time (TQUE) then initiates a
new transmission (new synchronization counter,
encrypted data) using the updated QUE value. Button
combinations are queued the same as individual but-
tons.
DS40035C-page 14
Preliminary
 2002 Microchip Technology Inc.