HCS500 Datasheet, PDF (15/24 Pages) Microchip Technology – KEELOQ CODE HOPPING ENCODER

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
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
encoder 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
CLK
µC DATA
LSB
TPP2TPP4
MSB LSB
MSB
MSB
LSB
MSB
TAW
DECODER DATA
Start Command
Command Byte
Configuration Byte Least Significant Byte
A
B
C
D
E
Most Significant Byte Acknowledge
F
G
H
© 1997 Microchip Technology Inc.
Preliminary
DS40153B-page 15