hcs500 Microchip Technology Inc., hcs500 Datasheet - Page 16

• Manufacturer Part Number: hcs500
• Description: Keeloq Code Hopping Decoder
• Manufacturer: Microchip Technology Inc.

HCS500
5.2
The programming command consists of the following:
• Command Request Sequence (A to B)
• Command Byte (B to C)
• Configuration Byte (C to D)
• Manufacturer’s Code Eight Data Bytes (D to G)
• Activation and Acknowledge Sequence (G to H)
FIGURE 5-1:
DS40153C-page 16
DECODER
C DATA
DATA
CLK
Programming Waveform
A
Start Command
T
PP
PROGRAMMING WAVEFORM
T
1
PP
2
T
T
PP
PP
4
3
B
LSB
T
CLKL
Command Byte
T
CLKH
MSB
T
CMD
C
LSB
Configuration Byte
T
DS
MSB
T
ADDR
D
Least Significant Byte
5.3
A total of 80 bits are clocked into the decoder. The 8-bit
command byte is clocked in first, followed by the 8-bit
configuration byte and the 64-bit manufacturer’s code.
The data must be clocked in Least Significant Bit (LSB)
first. The decoder will then encrypt the manufacturer’s
code using the decoder’s unique 64-bit EEPROM crypt
key. After completion of the programming EEPROM,
the decoder will acknowledge by taking the data line
high (G to H). If the data line goes high within 30 ms
after the clock goes high, programming also fails.
MSB
T
DATA
Programming Data String
E
F
LSB
Most Significant Byte
2002 Microchip Technology Inc.
MSB
T
DATA
G
Acknowledge
T
ACK
T
WT 2
H
T
AW