HCS410_01 Datasheet, PDF (17/36 Pages) Microchip Technology – KEELOQ® Code Hopping Encoder and Transponder

HCS410
2.6 IFF Special Features
2.6.1 ANTI-COLLISION (ACOLI)
When the ACOLI bit is set in the configuration word,
anti-collision mode is entered. The HCS410 will start
sending ACK pulses when it enters a magnetic field.
The ACK pulses stop as soon as the HCS410 detects
a start bit from the decoder. A ‘select encoder’ opcode
(00000) is then sent out by the decoder, followed by a
32-bit serial number. If the serial number matches the
HCS410’s serial number, the HCS410 will acknowl-
edge with the acknowledge sequence as shown in
Figure 2-18. The HCS410 can then be addressed as
normal. If the serial number does not match, the IFF
encoder will stop transmitting ACK pulses until it is
either removed from the field or the correct serial num-
ber is given.
FIGURE 2-18: SERIAL NUMBER CORRECT
ACKNOWLEDGE SEQUENCE
TE
LC0/1
3 TE
3 TE
TE
2.6.2 TRANSPONDER IN/RF OUT
When in transponder mode with ACOLI and XPRF set,
the outputs of the HCS410’s LC0:LC1 pins are echoed
on the PWM output line. After transmitting the data on
the LC pins, the data is then transmitted on the PWM
line. The transmission format mirrors a code hopping
transmission. The response replaces the 32-bit code
FIGURE 2-19:
LCI0/1
IFF INDUCTIVE IN RF OUT
Encoder
Select ACK
Opcode
(Read)
Response
(2*+16 bits)
hopping portion of the transmission. If the response is
a 16-bit response, the 16 bits are duplicated to make up
the 32-bit code hopping portion. The preamble, serial
number, CRC, and queuing bits are all transmitted as
normal (Figure 2-19).
This feature will be used in applications which use RF
for long distance unidirectional authentication and
short distance IFF.
Note:
If code word blanking is enabled, the
HCS410 will not give any ACK pulses after
a read, write or IFF.
2.6.3 INTELLIGENT DAMPING
If the LC circuit on the transponder has a high Q-factor,
the circuit will keep on resonating for a long time after
the field has been shut down by the decoder. This
makes fast communication from the decoder to the
HCS410 difficult. If the IDAMP bit is set to 0, the
HCS410 will clamp the LC pins for 5 µs every 1/4 TE,
whenever the HCS410 is expecting data from the
decoder. The intelligent dumping pulses start 64 TE
after the acknowledge pulses have been sent and con-
tinue for 64 TE. If the HSC410 detects data from the
base station while sending out dump pulses, the dump
pulses will continue to be sent. This option can be set
in the configuration word.
2.7 LED Indicator
If a signal is detected on LC0, the LED pin goes high for
30 ms every 8s (IFFB = 0) or 4s (IFFB 1) to indicate that
the power source is charging.
Next
Ack
PWM
Preamble
Response Fixed Code
Header ^{(32 bits) (37 bits)}
*2-bit preamble precedes the data.
32-bit Response
16-bit
16-bit
Response Response
FIGURE 2-20: LED INDICATOR WHEN CHARGING POWER SOURCE
LC0
LED
IFFB = 0
LED
IFFB = 1
4s
2s
4s
8s
30 ms
30 ms
*Patents have been applied for.
 2001 Microchip Technology Inc.
Preliminary
DS40158E-page 17