HCS412I MICROCHIP [Microchip Technology], HCS412I Datasheet - Page 27

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

4.3.8
The ENABLE DEFAULT IFF COMMUNICATION com-
mand defaults certain HCS412 communication options
such that the transponder reader may communicate to
the device with a common (safe) protocol. The default
setting remains for the duration of the communication,
returning to normal only after a device RESET.
TABLE 4-9:
FIGURE 4-14: ENABLE DEFAULT IFF COMMUNICATION
4.4
TABLE 4-10:
4.4.1
Enabling the Proximity Activation configuration option
allows the HCS412 to transmit a hopping code trans-
mission in response to a signal present on the LC0 pin.
FIGURE 4-15: PROXIMITY ACTIVATION
Inductive
Command
LFSP1:0
LF Communication from reader to HCS412
LF Communication from HCS412 to reader
DATA (RF)
2002 Microchip Technology Inc.
(LF)
11100
Communication from reader to HCS412
Communication from HCS412 to reader
00
01
10
11
Inductive Comms
ENABLE DEFAULT IFF COMMUNICATION
IFF Communication Special Features
PASSIVE PROXIMITY ACTIVATION
(LFSP = 10)
RF Comms
ACK
Enable default IFF communication
Anticollision enabled (Section 4.3.1)
Anticollision and RF Echo enabled
DEFAULT IFF COMMUNICATION COMMANDS
LF COMMUNICATION
SPECIAL FEATURES (LFSP)
Proximity Activation enabled
No special options enabled
No command received from
Activate
Field
Description
reader for 255 LF
Description
pulses
ACK
ACK
TE
Command
.
Delay to
2 LF
Start
T
ATO
TE
Preliminary
Command
Command
Expected data In
Default IFF communication settings:
• Anticollision disabled
• RF echo disabled
• 200 s LF baud rate.
The HCS412 sends out Field Acknowledge Sequence
in response to detecting the LF field (Figure 4-1). If the
HCS412 does not receive a command before the sec-
ond field Acknowledge sequence [within 255 LFT
will transmit a normal code hopping transmission for 2
seconds on the DATA pin. After 2 seconds the HCS412
reverts to normal transponder mode.
The 2 second transmission does not repeat when the
device is in the presence of a continuous LF field. The
HCS412 must be RESET, remove and reapply the LF
field, to activate another transmission.
The button status used in the code hopping transmis-
sion indicates a proximity activation by clearing the S0,
S1 and S2 button activation flags.
None
Delay
Transmit hopping code for 2
Next Command
seconds
Response
HCS412
None
DS41099C-page 27
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