HCS515-IP Microchip Technology, HCS515-IP Datasheet - Page 7

• Manufacturer Part Number: HCS515-IP
• Description: KEELOQ CODE HOPPING DECODER
• Manufacturer: Microchip Technology

4.0
The HCS515 interfaces to a microcontroller via a syn-
chronous serial interface. A clock and data line are
used to communicate with the HCS515. The microcon-
troller controls the clock line. There are two groups of
data transfer messages. The first is from the decoder
whenever the decoder receives a valid transmission.
The decoder signals reception of a valid code by taking
the data line high (maximum of 500 ms) The microcon-
troller then services the request by clocking out a data
string from the decoder. The data string contains the
function code, the status bit, and block indicators. The
second is from the controlling microcontroller to the
decoder in the form of a defined command set.
Figure 4-1 shows the HCS515 decoder and the I/O
interface lines necessary to interface to a microcontrol-
ler.
FIGURE 4-1:
FIGURE 4-2:
S_CLK
S_DAT
1998 Microchip Technology Inc.
A
INTERFACING TO A
MICROCONTROLLER
Decoder Signal Valid
T
CLA
Transmission
T
DHI
T
V
ACK
CC
HCS515 DECODER AND I/O INTERFACE LINES
DECODER VALID TRANSMISSION MESSAGE
T
CLKH
T
ACT
B
X
X
X
0
REPT V
1
2
3
4
5
6
7
NC
NC
V
S0
S1
MCLR
NC
DD
T
LOW
CLKL
S0
HCS515
T
CLKH
S1
Preliminary
S_CLK
S2
S_DAT
RF_IN
V
Information
NC
NC
NC
SS
S3
14
13
12
11
10
9
8
T
DS
1
4.1
The decoder informs the microcontroller of a valid
transmission by taking the data line high for up to
500 ms. The controlling microcontroller must acknowl-
edge by taking the clock line high. The decoder then
takes the data line low. The microcontroller can then
begin clocking a data stream out of the HCS515. The
data stream consists of:
• Start bit ‘0’.
• 2 status bits [REPEAT, VLOW].
• 4-bit function code [S3 S2 S1 S0].
• Stop bit ‘1’.
• 4 bits indicating the number of transmitters
• 4 bits indicating which block was used
• 64 bits of the received transmission with the hop-
The decoder will terminate the transmission of the data
stream at any point where the clock is kept low for
longer than 1 ms.Therefore, the microcontroller can
only clock out the required bits. A maximum of 80 bits
can be clocked out of the decoder.
CNT0
learned into the decoder [CNT3…CNT0].
[TX3…TX0].
ping code decrypted.
Note:
X
X
X
Valid Transmission Message
CNT3
Data is always clocked in/out Least
Significant Bit (LSB) first.
TX0
TX3
Ci
RX0
Received String
RX1
MICRO RESET
SYNC CLOCK
HCS515
S1 OUTPUT
S0 OUTPUT
SYNC DATA
RF DATA
DS40183A-page 7
RX62
RX63
Cii