HCS473 Datasheet, PDF (9/68 Pages) Microchip Technology – Code Hopping Encoder and Transponder

FIGURE 2-6:
LED PIN DIAGRAM
VDD
Weak
LED
LED
Program
Mode
HV
Detect
FIGURE 2-7:
LCCOM/LCX/LCY/LCZ/
VSST PIN DIAGRAM
LCX
only
RECTIFIER and
REGULATOR
VSST
LCX/LCY/
LCZ Inputs
100Ω
10V
AMP
and
DET
LC
Input
DAMP
LCCOM
100Ω
10V
CLAMP
R_DAMP
BIAS
CURRENT
HCS473
2.3 Architectural Overview
2.3.1 WAKE-UP LOGIC
The HCS473 automatically goes into a low-power
Standby mode once connected to a supply voltage.
Power is supplied to the minimum circuitry required to
detect a wake-up condition; button activation or LC sig-
nal detection.
The HCS473 will wake from Low-power mode when a
button input is pulled high or a signal is detected on a
LC low frequency antenna input pin. Waking involves
powering the main logic circuitry that controls device
operation. The button and transponder inputs are then
sampled to determine which input activated the device.
A button input activation places the device into Encoder
mode. A signal detected on the transponder input
places the device into Transponder mode. Encoder
mode has priority over Transponder mode such that
communication on the transponder input would be
ignored or perhaps interrupted if it occurred simulta-
neously to a button activation; ignored until the button
input is released.
2.3.2 ENCODER INTERFACE
Using the four button inputs, up to 15 unique control
codes may be transmitted.
Note: S3 may not be used as a button input if the
RFEN option is enabled.
 2002 Microchip Technology Inc.
Preliminary
DS40035C-page 7