HCS412_11 Datasheet, PDF (19/52 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder and Transponder Burglar alarm systems

HCS412
FIGURE 4-1: FIELD ACKNOWLEDGE SEQUENCE
3LFTE 3LFTE 3LFTE
T_PU
Inductive
Comms
(LC)
8LFTE
2LFTE
T_ATO
Command
RF
Comms
(DATA)
8LFTE
Field Ack sequence repeats every 255 LFTE if no command is received.
Inductive
Comms
(LC)
255LFTE
255LFTE
RF
Comms
(DATA)
Communication from reader to HCS412
Filed ACK Sequence from HCS412 to reader
FIGURE 4-2: LC PIN PULSE POSITION MODULATION (PPM)
Transponder reader communication to the HCS412
0
Start or
previous
bit
2 LFTE 2 LFTE
T_BITC
1
Extending the high time
is acceptable but the low
time should minimally
be 1 LF_TE.
The HCS412 determines
bit values from rising edge
to rising edge times.
4 LFTE
T_BITC
2 LFTE
HCS412 response back to the reader
0
Start or ^{LFTE LFTE}
previous
bit
T_BITR
1
2 LFTE LFTE
T_BITR
© 2011 Microchip Technology Inc.
DS41099D-page 19