HCS410T-P datasheet(7/36 Pages) MICROCHIP

7 / 36 page

HCS410

 2001 Microchip Technology Inc.

Preliminary

DS40158E-page 7

2.2

Code Hopping Mode (CH Mode)

The HCS410 wakes up upon detecting a switch closure

and then delays approximately 30 ms for switch

debounce (Figure 2-7). The synchronization counter

value, fixed information, and switch information are

encrypted to form the code hopping portion. The

encrypted or code hopping portion of the transmission

changes every time a button is pressed, even if the

same button is pushed again. Keeping a button

pressed for a long time results in the same code word

being transmitted until the button is released or time-

out occurs. A code that has been transmitted will not

occur again for more than 64K transmissions. Overflow

information programmed into the encoder can be used

by the decoder to extend the number of unique trans-

missions to more than 192K.

If, during the transmit process, it is detected that a new

button(s) has been added, a reset will immediately be

forced and the 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 current code word will be completed

and the power down will occur. If, after a button combi-

nation is pressed, and the same button combination is

pressed again within 2 seconds of the first press, the

current transmission will be aborted and a new trans-

FIGURE 2-7:

CODE HOPPING ENCODER OPERATION

20-second

time-out

Transmitted

2 second

time-out

completed?

All buttons

released?

Sample Inputs

Update Sync Info

Encrypt With

Transmit

Encoder Key

Power-up

(A button has been

pressed (Note1))

Buttons added?

Yes

(Note 1)

7 complete code

words?

Complete current

code word while

checking buttons

(Note 2)

Stop transmitting

DINC Set?

Power down

Buttons

pressed?

(Note 1)

Same as

press?

Increment queue

counter

20 second

time-out

completed?

Buttons

pressed?

(Note 1)

Increase sync

counter

by 12

immediately

Yes

Note 1: 30 ms debounce on press and release of all buttons.

2: Completes a minimum of 3 code words if MTX3 is set.

DINC

Set?

Yes

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