HCS500-I Datasheet, PDF (16/34 Pages) Microchip Technology – KEELOQ Code Hopping Decoder

HCS500
5.2 Programming Waveform
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: PROGRAMMING WAVEFORM
TCLKL
TCMD
TADDR
TPP1 TPP3
TCLKH
TDS
CLK
5.3 Programming Data String
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.
TDATA
TDATA TACK
TWT2
µC DATA
LSB
TPP2TPP4
MSB
LSB
MSB
MSB
DECODER
DATA
Start Command Command Byte
Configuration Byte Least Significant Byte
A
B
C
D
E
LSB
MSB
TAW
Most Significant Byte Acknowledge
F
G
H
DS40153C-page 16
© 2002 Microchip Technology Inc.