HCS410 datasheet(18/36 Pages) MICROCHIP

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HCS410

DS40158C-page 18

Preliminary

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 2-19. 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 2-19: SERIAL NUMBER CORRECT

ACKNOWLEDGE SEQUENCE

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

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 2-18).

This feature will be used in applications which use RF

for long distance unidirectional authentication and

short distance 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. Refer to Figure 2-18 for timing details. 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.

FIGURE 2-20: LED INDICATOR WHEN CHARGING POWER SOURCE

LC0/1

3 TE

LC0

LED

IFFB = 0

LED

IFFB = 1

30 ms

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