HCS412I MICROCHIP [Microchip Technology], HCS412I Datasheet - Page 26

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

HCS412
FIGURE 4-11: IFF CHALLENGE AND RESPONSE
4.3.7
The command tells the HCS412 to increment the syn-
chronization counter and build the 32-bit code hopping
portion of the code word.
• If RF Echo is disabled, the data will be transmitted
TABLE 4-8:
FIGURE 4-12: CODE HOPPING REQUEST (RF ECHO DISABLED)
FIGURE 4-13: CODE HOPPING REQUEST (RF ECHO ENABLED)
DS41099C-page 26
Command
Inductive (LF)
DATA (RF)
on the LC lines only (Figure 4-12).
Communication from reader to HCS412
Communication from HCS412 to reader
Communication from reader to HCS412
Communication from HCS412 to reader
LF Communication from reader to HCS412
LF Communication from HCS412 to reader
11000
CODE HOPPING REQUEST
Field
ACK
Request Hopping Code transmission
Activate
Field
T
Activate
PU
Field
REQUEST HOPPING CODE COMMANDS
T
PU
ACK
ACK
ACK
ACK
Description
Command
Delay to
2 LF
Start
T
Command
ATO
Delay to
TE
T
ATO
2 LF
Start
TE
Command
Command
Preliminary
Command
Command
Delay to
2 LF
Start
Data
T
Expected data In
OTD
TE
• If RF Echo is enabled, the data will be transmitted
The data format will be the same as described in
Section 3.2.
in a code word on the DATA line followed by the
data transmitted on the LC lines. The DATA line is
transmitted first for passive entry support
(Figure 4-13).
None
Delay before
Response
32-bit Challenge
T
OTH
Challenge
1 LF
Start
32-bit
TE
0 1
32-bit Response
Delay before
Response
32-Bit Hopping Code
32-Bit PPM
Response
T
1 LF
Start
01b Preamble
IT
2002 Microchip Technology Inc.
TE
Response
32-Bit PPM
0 1
Response
Response
32-bit
Response
32-bit
01b Preamble
Field
ACK