HCS362-I Datasheet, PDF (14/38 Pages) Microchip Technology – KEELOQ Code Hopping Encoder

HCS362
3.4 RF Enable and PLL Interface
The S3/RFEN pin of the HCS362 can be configured to
function as an RF Enable output signal. This is selected
by the RF Enable Output (RFEN) configuration option.
When enabled, this pin will be driven HIGH before data
is transmitted through the DATA pin.
The RF Enable and DATA output are synchronized so
to interface with RF PLL circuits operating in ASK
mode. Figure 3-10 shows the startup sequence. The
RFEN signal will go LOW at the end of the last code
word, including the Guard time.
When the RF Enable output is selected, the S3 pin can
still be used as a button input. The debouncing logic will
be affected though, considerably reducing the respon-
siveness of the button input.
FIGURE 3-10: PLL INTERFACE
Button Press
S[3210]
RFEN
Note:
When the RF Enable output feature is used
and a four (or more) buttons input configu-
ration is required, the use of a scheme sim-
ilar to Figure 2-1 (scheme C) is
recommended.
Button Release
DATA
TRFON
TTD
1st CODE WORD
TG
2nd CODE WORD
Guard Time
DS40189D-page 14
Preliminary
© 2002 Microchip Technology Inc.