hcs512 Microchip Technology Inc., hcs512 Datasheet - Page 5

• Manufacturer Part Number: hcs512
• Description: Keeloq Code Hopping Decoder Keeloq Code Hopping Decoder
• Manufacturer: Microchip Technology Inc.

3.0
3.1
The HCS512 activates the S3, S2, S1 & S0 outputs
when a new valid code is received. The outputs will be
activated for approximately 500 ms. If a repeated code
is received during this time, the output extends for
approximately 500 ms.
3.2
The decoder has a PWM/Synchronous interface con-
nection to microcontrollers with limited I/O. An output
data stream is generated when a valid transmission is
received. The data stream consists of one START bit,
four function bits, one bit for battery status, one bit to
indicate a repeated transmission, two status bits, and
one STOP bit. (Table 3-1). The DATA and CLK lines are
used to send a synchronous event message.
FIGURE 3-1:
FIGURE 3-2:
A 1-wire PWM or 2-wire synchronous interface can be used.
In 1-wire mode, the data is transmitted as a PWM signal with a basic pulse width of 400 s.
In 2-wire mode, Synchronous mode PWM bits start on the rising edge of the clock, and the bits must be sampled on the
falling edge. The START bit is a ‘1’ and the STOP bit is ‘0’.
FIGURE 3-2:
Note:
2002 Microchip Technology Inc.
START
START
CLK
DATA
DESCRIPTION OF FUNCTIONS
Parallel Interface
Serial Interface
The Decoder output PWM format logic (“1” / “0”) is reversed with respect of the Encoder modulation format.
DATA OUTPUT FORMAT
STATUS MESSAGE FORMAT
PWM OUTPUT FORMAT
S3
0
600 s
START
1200 s
S2
0
S3
S1
S2
0
(1)
S1
S0
0
RESULT
S0
V
LOW
A special status message is transmitted on the second
pass of learn. This allows the controlling microcontrol-
ler to determine if the learn was successful (Result = 1)
and if a previous transmitter was overwritten (Overwrite
= 1). The status message is shown in Figure 3-2.
Table 3-1 show the values for TX1:0 and the number of
transmitters learned.
TABLE 3-1:
V
TX1
LOGIC “1”
LOGIC “0”
LOW
0
0
1
1
OVRWR
REPEAT
RPT
1/31/3 1/3
1200 s
STATUS BITS
TX0
0
1
0
1
Reserved Reserved
TX1
TX1
Number of Transmitters
TX0
TX0
HCS512
DS40151D-page 5
Three
Four
One
Two
STOP
STOP
STOP