HCS365 Datasheet, PDF (5/34 Pages) Microchip Technology – KEELOQ Code Hopping Encoder

2.0 DEVICE DESCRIPTION
As shown in the typical application circuits (Figure 2-1),
the HCS365 is an easy device to use. It requires only
the addition of buttons and RF circuitry for use as the
encoder in your security application. A description of
each pin is described in Table 2-1. Refer to Figure 2-2
for information on the I/O pins.
Note:
S0-S3 inputs have pull-down resistors. VIN
should be tied high if the step-up regulator
is not used.
TABLE 2-1: PIN DESCRIPTIONS
Name
S0
S1
S2
S3/
SHIFT/
RFEN
VSS
DATA
LED
VDD
Pin
Number
Description
1 Switch input 0
2 Switch input 1
3 Switch input 2
4 Switch input 3,
SHIFT button or
RF Enable output
5 Ground reference
6 Data output pin/
7 Open drain output for LED
8 Positive supply voltage
HCS365
The HCS365 will normally be in a low power SLEEP
mode. When a button input is taken high, the device will
wake up, start the step-up regulator, and go through the
button debounce delay of TDB before the button code is
latched. In addition, the device will then read the con-
figuration options. Depending on the configuration
options and the button code, the device will determine
what the data and modulation format will be for the
transmission. The transmission will consist of a stream
of code words and will be transmitted TPU after the but-
ton is pressed for as long as the buttons are held down
or until a time-out occurs. The code word format can be
either a code hopping format or a seed format.
The time-out time can be selected with the Time-out
Select (TSEL) configuration option. This option allows
the time-out to be set to 0.8s, 3.2s, 12.8s, or 25.6s.
When a time-out occurs, the device will go into SLEEP
mode to protect the battery from draining when a button
gets stuck.
If the device is in the transmit process and detects that
a new button is pressed, the current code word will be
aborted, a new code word will be transmitted and the
time-out counter will RESET. If all the buttons are
released, a minimum number of code words will still be
completed. The minimum code words can be set to 1,
2, 4, or 8 using the Minimum Code Words (MTX) con-
figuration option. If the time for transmitting the mini-
mum code words is longer than the time-out time, the
device will not complete the minimum code words.
© 2002 Microchip Technology Inc.
Preliminary
DS41109D-page 5