HCS300-IP Microchip Technology, HCS300-IP Datasheet - Page 11

• Manufacturer Part Number: HCS300-IP
• Description: KEE LOQ Code Hopping Encoder
• Manufacturer: Microchip Technology

6.0
When using the HCS300 in a system, the user will have
to program some parameters into the device including
the serial number and the secret key before it can be
used. The programming cycle allows the user to input
all 192 bits in a serial data stream, which are then
stored internally in EEPROM. Programming will be
initiated by forcing the PWM line high, after the S3 line
has been held high for the appropriate length of time
line (Table 6-1 and Figure 6-1). After the program mode
is entered, a delay must be provided to the device for
the automatic bulk write cycle to complete. This will
write all locations in the EEPROM to an all zeros pat-
tern. The device can then be programmed by clocking
in 16 bits at a time, using S3 as the clock line and PWM
as the data in line. After each 16-bit word is loaded, a
programming delay is required for the internal program
FIGURE 6-1:
FIGURE 6-2:
(Clock)
(Clock)
Note 1: Unused button inputs to be held to ground during the entire programming sequence.
Note 2: The V
(Data)
(Data)
1996 Microchip Technology Inc.
PWM
PWM
S3
S3
Note: If a Verify operation is to be done, then it must immediately follow the Program cycle.
PROGRAMMING THE HCS300
Programming Cycle
Enter Program
Bit190
T
PS
Mode
DD
End of
Bit191
T
PROGRAMMING WAVEFORMS
VERIFY WAVEFORMS
pin must be taken to ground after a program/verify cycle.
PH
1
T
PH
T
2
WC
T
PBW
Begin Verify Cycle Here
T
Bit 0
CLKH
Bit 0
T
CLKL
Bit 1
Bit 1 Bit 2
T
Bit 2
DS
T
Preliminary
DV
Repeat 12 times for each word
T
Bit 3
DH
Data for Word 0 (KEY_0)
Bit 3
Data in Word 0
cycle to complete. This delay can take up to Twc. At the
end of the programming cycle, the device can be veri-
fied (Figure 6-2) by reading back the EEPROM. Read-
ing is done by clocking the S3 line and reading the data
bits on PWM. For security reasons, it is not possible to
execute a verify function without first programming the
EEPROM. A verify operation can only be done
once, immediately following the program cycle.
Bit 14
Note:
Bit 14
Bit 15
To ensure that the device does not acci-
dentally enter programming mode, PWM
should never be pulled high by the circuit
connected to it. Special care should be
taken when driving PNP RF transistors.
Bit 15
T
Bit 16 Bit 17
WC
HCS300
DS21137D-page 11
Data for Word 1
Bit 16
Bit190 Bit191
Bit 17