HCS300 datasheet(5/36 Pages) MICROCHIP

5 / 36 page

DS21137G-page 5

HCS300

2.0

ENCODER OPERATION

As shown in the typical application circuits (Figure 2-1),

the HCS300 is a simple device to use. It requires only

the addition of buttons and RF circuitry for use as the

transmitter in your security application. A description of

each pin is given in Table 2-1.

FIGURE 2-1:

TYPICAL CIRCUITS

TABLE 2-1:

PIN DESCRIPTIONS

The HCS300 will wake-up upon detecting a button

press and delay approximately 10 ms for button

debounce (Figure 2-2). The synchronization counter,

discrimination value and button information will be

encrypted to form the hopping code. The hopping code

portion will change every transmission, even if the

same button is pushed again. A code word that has

been transmitted will not repeat for more than 64K

transmissions. This provides more than 18 years of use

before a code is repeated; based on 10 operations per

day. Overflow information sent from the encoder can be

used to extend the number of unique transmissions to

more than 192K.

If in the transmit process it is detected that a new but-

ton(s) has been pressed, a RESET will immediately

occur and the current code word will not be completed.

Please note that buttons removed will not have any

effect on the code word unless no buttons remain

pressed; in which case the code word will be completed

and the power-down will occur.

FIGURE 2-2:

ENCODER OPERATION

Name

Number

Description

Switch input 0

Switch input 1

Switch input 2 / Clock pin when in

Programming mode

Switch input 3

VSS

Ground reference

PWM

Pulse Width Modulation (PWM)

output pin / Data pin for

Programming mode

LED

Cathode connection for LED

VDD

Positive supply voltage

VDD

Tx out

LED

VDD

PWM

Vss

2 button remote control

VDD

Tx out

LED

VDD

PWM

Vss

5 button remote control (Note)

B4 B3 B2 B1 B0

Note:

Up to 15 functions can be implemented

by pressing more than one button

simultaneously or by using a suitable

diode array.

Power-Up

RESET and Debounce Delay

(10 ms)

Sample Inputs

Update Sync Info

Encrypt With

Load Transmit Register

Buttons

Added

All

Buttons

Released

(A button has been pressed)

Transmit

Stop

Yes

Crypt Key

Complete Code

Word Transmission

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