HCS412I MICROCHIP [Microchip Technology], HCS412I Datasheet - Page 22

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

HCS412
4.3.2
The transponder reader sends one of seven possible
read commands indicating which 16-bit EEPROM word
to retrieve (Table 4-4). The HCS412 retrieves the data
and returns the 16-bit response.
Each Read response is preceded by a 1LF
START pulse and ‘01b’ preamble (Figure 4-4).
TABLE 4-4:
FIGURE 4-4:
4.3.3
The transponder reader sends one of seven possible
write commands (Table 4-5) indicating which 16-bit
EEPROM word to write to. The 16-bit data to be written
follows the command. The HCS412 will attempt to write
the value into EEPROM and respond with an Acknowl-
edge sequence if successful.
The following locations are available to write:
• The 64-bit general purpose user EEPROM.
• The 32-bit serial number (SER[1:0]). The serial
• The16-bit Configuration word containing all non-
DS41099C-page 22
Command
Communication from reader to HCS412
Communication from HCS412 to reader
(USER[3:0]) (Figure 4-6).
number is also transmitted in each code hopping
transmission (Figure 4-5).
security related configuration options. If the con-
figuration is written, the device must be RESET
before the new settings take effect (Figure 4-5).
00001
00010
00011
00100
00101
00110
00111
READ
WRITE
LIST OF READ COMMANDS
Read Configuration word
READ
Read high serial number
Read low serial number
Read user EEPROM 0
Read user EEPROM 1
Read user EEPROM 2
Read user EEPROM 3
Activate
Description
Field
T
PU
ACK
ACK
Command
Delay to
2 LF
T
Start
ATO
TE
TE
Preliminary
low
Expected data In
Command
Command
None
None
None
None
None
None
None
The following locations are available to read:
• The 64-bit general purpose user EEPROM.
• The 32-bit serial number (SER[1:0]). The serial
• The16-bit Configuration word containing all non-
A Transport Code, write access password, protects the
serial number and configuration word from undesired
modification. For these locations the reader must follow
the WRITE command with the appropriate 28-bit trans-
port code, then the 16 bits of data to write. Only a cor-
rect match with the transport code programmed during
production will allow write access to the serial number
and configuration word (Figure 4-5).
The delay to a successful write Acknowledge will vary
depending on the number of bits changed.
(USER[3:0]).
number is also transmitted in each code hopping
transmission.
security related options.
Delay until
Response
T
1 LF
Start
RT
TE
Higher 16 bits of serial number (SER1)
Lower 16 bits of serial number (SER0)
16 Bits of User EEPROM USR0
16 Bits of User EEPROM USR1
16 Bits of User EEPROM USR2
16 Bits of User EEPROM USR3
0 1
16-bit Configuration word
16-bit Response
01b Preamble
Response
2002 Microchip Technology Inc.
16-bit
Response
6 LF
TE