HCS412I MICROCHIP [Microchip Technology], HCS412I Datasheet - Page 29

• Manufacturer Part Number: HCS412I
• Description: KEELOQ Code Hopping Encoder and Transponder
• Manufacturer: MICROCHIP [Microchip Technology]

4.4.3
A high Q-factor LC antenna circuit connected to the
HCS412 will continue to resonate after a strong LF field
is removed, slowly decaying. The slow decay makes
fast communication near the reader difficult as data bit
low times disappear.
If the Intelligent Damping option is enabled, the
HCS412 will clamp the LC pins through a 2 k resistor
for 5
expecting data from the transponder reader. The intel-
ligent damping pulses start 12.5 LF
Acknowledge sequence is complete and continue for
12.5 LF
while sending out damping pulses, it will continue to
send the damping pulses.
TABLE 4-11:
TABLE 4-12:
Time Element
Power-up Time
Acknowledge to Opcode Time
PPM Command Bit Time
PPM Response Bit Time
Read Response Time
IFF Response Time
Opcode to Data Input Time
Transport Code to Data Input Time
Encoder Select Acknowledge Time
IFF EEPROM Write Time (16 bits)
Op Code to Hop Code Response Time
2002 Microchip Technology Inc.
IDAMP
0
1
s every 1/4 LF
TE
INTELLIGENT DAMPING (IDAMP)
. If the HCS412 detects data from the reader
INTELLIGENT DAMPING
(IDAMP)
LF TIMING SPECIFICATIONS
Intelligent damping disabled
Parameter
Intelligent damping enabled
TE
, whenever the HCS412 is
Description
IFFB = 0
IFFB = 1
Data = 0
Data = 1
Data = 0
Data = 1
TE
after the
Preliminary
Symbol
T
T
LF
T
T
T
T
T
T
T
T
BITC
BITR
T
ATO
OTD
ESA
OTH
TTD
WR
PU
RT
IT
TE
FIGURE 4-19: INTELLIGENT DAMPING
10.26
Min.
3.87
180
4.2
2.6
2.2
90
13
—
—
—
—
—
—
—
Field
ACK
LF
TE
Typ.
11.4
200
100
4.3
13
30
—
—
6
4
6
2
3
DAMP PULSES
+100
Bit From
12.5 LF
reader
5 s
TE
12.54
Max.
4.73
HCS412
220
110
7.8
—
—
—
—
—
—
—
—
—
12.5 LF
DS41099C-page 29
1/4 LF
TE
TE
Units
LF
LF
LF
LF
ms
ms
ms
ms
ms
ms
5 s
s
s
TE
TE
TE
TE