HCS473T-I/SN Microchip Technology, HCS473T-I/SN Datasheet - Page 28

• Manufacturer Part Number: HCS473T-I/SN
• Description: IC KEELOQ 3AXIS TRANSCODER 8SOIC
• Manufacturer: Microchip Technology
• Series: KEELOQ®r
• Type: Code Hopping Encoder and Transponderr

Specifications of HCS473T-I/SN

• Applications: Access Control Systems
• Mounting Type: Surface Mount
• Package / Case: *
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification

HCS473
3.2.3.3
The HCS473 can perform a 16-bit or 32-bit challenge
and response (IFF) based on the K
algorithm.
The transponder reader follows the 3-bit IFF command
with one of four possible options indicating a 16 or 32-
bit challenge and whether to use the encoder or tran-
sponder crypto key to create the response (Table 3-5).
The 3-bit option is followed by the appropriate 16 or 32-
bit challenge; typically a random number. The
sequence ends with a CRC calculated over the com-
mand, option and challenge bits, (Figure 3-14).
The HCS473 encrypts the challenge using the desig-
nated crypto key and responds with a 32-bit result. The
reader authenticates the response by decrypting it and
verifying it matches the original challenge.
FIGURE 3-14:
DS40035C-page 26
Inductive In
RF Response
(LC Pins)
(DATA Pin)
Previous Command
Wake Sequence
Response
or
IFF CHALLENGE AND RESPONSE
T
SF
ACK
IFF SEQUENCE (RF RESPONSE EXAMPLE)
T
CMD
T
CMD
Command
T
CMD
‘010
CMD
EE
L
OQ
2
’ 3 bits
Option
encryption
OPT
Preliminary
16/32
CHAL
bits
Challenge
16/32-Bit
2 bits
CRC
If 16-bit IFF is selected, the 32-bit response consists of
two copies of the 16-bit challenge.
RFRSP determines if the response will be transmitted
on the DATA pin. If enabled, the response will follow the
selected Encoder mode code hopping format with the
hopping code replaced with the 32-bit response. The
transmissions will contain a button code of ‘0000’.
LFRSP determines if the response will be transmitted
on the LC pins. The LC pin response will be the 32-bit
result, modulated PPM format.
If both RFRSP and LFRSP are enabled, the HCS473
will send the response on the DATA pin immediately fol-
lowed by the PPM response on the LC pins. Refer to
Section 3.2.1.7 for further response path details.
The next command must begin T
response.
CRC
T
IFF
T
RESPONSE
FINH
T
IFF
LF must remain on if following
with consecutive command
or if waiting for LF response
 2002 Microchip Technology Inc.
RF Response (RFRSP=1)
T
CMD
Optional Next
Command
CMD
after the