MCS3142-ISLASHST datasheet(16/37 Pages) MICROCHIP

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MCS3142

DS40001747A-page 16

 2014 Microchip Technology Inc.

4.0

CLASSIC KEELOQ®

TECHNOLOGY OPERATION

4.1

Synchronization Counter

This is the 16-bit synchronization value that is used to

create the hopping code for transmission. This value

will be incremented after every transmission. The initial

value of the synchronization counter may be set via the

Synchronization Counter Initial Value registers (see

Table 3-22).

4.2

DISC Bits

The Discrimination bits are used to validate the

decrypted code word. The discrimination value is

typically programmed with the ten Least Significant bits

of the serial number or some other fixed value, as

desired by the manufacturer.

The Discrimination bits are programmed into the

Configuration registers at program-time. SeeTable 3-5.

4.3

Function Code (Button Status

Code)

The function code is a bitmapped representation of the

state of each button on the transmitter. States are

active-high.

4.4

Serial Number

Each Classic KEELOQ encoder transmits its 28-bit serial

number with each transmission. It is intended that this

serial number be unique to a system. It is set in the

Serial Number Configuration registers, described in

Table 3-4.

TABLE 4-1:

CLASSIC KEELOQ® BUTTON

CODE TRANSLATION

Button

Function Code

xxx1

xx1x

x1xx

1xxx

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