HCS512_11 Datasheet, PDF (4/34 Pages) Microchip Technology – KEELOQ® Code Hopping Decoder system and high security

HCS512
FIGURE 1-3:
BASIC OPERATION OF RECEIVER (DECODER)
1 Received Information
Button Press
Information
Serial Number
32 Bits of
Encrypted Data
EEPROM Array
Manufacturer Code
2
Check for
Match
3
KEELOQ®
Decryption
Algorithm
Serial Number
Sync Counter
Crypt Key
Perform Function
5
Indicated by
button press
Decrypted
Synchronization
Counter
4
Check for
Match
NOTE: Circled numbers indicate the order of execution.
2.0 PIN ASSIGNMENT
PIN
Decoder
Function
I/O ⁽¹⁾
Buffer
Type⁽¹⁾
Description
1
LRNIN
I
TTL
Learn input - initiates learning, 10K pull-up required on input
2
LRNOUT
O
TTL
Learn output - indicates learning
3
NC
—
TTL
Do not connect
4
MCLR
I
ST
Master clear input
5
Ground
P
—
Ground connection
6
S0
O
TTL
Switch 0
7
S1
O
TTL
Switch 1
8
S2
O
TTL
Switch 2
9
S3
O
TTL
Switch 3
10
VLOW
O
TTL
Battery low indication output
11
SLEEP
I
TTL
Connect to RFIN to allow wake-up from SLEEP
12
CLK
I/O
TTL/ST ⁽²⁾
Clock in Programming mode and Synchronous mode
13
DATA
I/O
TTL/ST ⁽²⁾
Data in Programming mode and Synchronous mode
14
VDD
P
—
Power connection
15 OSCOUT (1MHZ)
O
TTL
Oscillator out (test point)
16 OSCIN (4MHz)
I
ST
Oscillator in – recommended values 4.7 kΩ and 22 pF
17
NC
—
—
18
RFIN
I
TTL
RF input from receiver
Note 1: P = power, I = in, O = out, and ST = Schmitt Trigger input.
2: Pin 12 and Pin 13 have a dual purpose. After RESET, these pins are used to determine if Programming
mode is selected in which case they are the clock and data lines. In normal operation, they are the clock
and data lines of the synchronous data output stream.
DS40151E-page 4
© 2011 Microchip Technology Inc.