MCS3142-ISLASHST datasheet(26/37 Pages) MICROCHIP

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MCS3142

DS40001747A-page 26

 2014 Microchip Technology Inc.

7.3

Code Word Completion

MCS3142 always ensures that a full and complete

code word is transmitted even if all buttons are

released before transmission is complete. Multiple

code words may be transmitted after release to comply

with the minimum code word configuration option.

7.4

Minimum and Maximum Code

Word

The Minimum and Maximum Code Word feature places

boundaries on the total duration of a transmission.

This feature is configured by setting the number of

code words for a given encoder. The device will always

transmit a complete code word. Because the code

word durations are fixed and known, it is possible to

convert code word counts into a duration time.

Code word duration is fixed and based on the selected

bit rate, data encoding method and encoder type. As

described in Section 6.1 “Data Modulation Format

and Baud Rate”, all timing is derived from TE, the Time

Element, which describes the duration of a single

element of transmission. A Manchester-encoded signal

has two TE per bit; a PWM-encoded signal has three TE

per bit.

This feature is configured with the Minimum and

Maximum Code Words Count Configuration registers

(see Table 3-8 for the Classic KEELOQ encoder and

Table 3-16 for the Ultimate KEELOQ encoder). Table 7-2

defines equations to convert code word length into time.

7.5

Blank Alternate Code Word

The Blank Alternate Code Word feature may be used to

reduce the average power of a transmission by

transmitting only every second or every fourth code word.

Enabling this option may allow the manufacturer to

transmit a higher amplitude transmission as the

time-averaged power is reduced. This feature is

configured in the Encoder Configuration registers, see

Table 3-6 for the Classic KEELOQ encoder and Table 3-14

for the Ultimate KEELOQ encoder.

TABLE 7-2:

TRANSMISSION DURATION EQUATIONS

Encoder Type

Data Encoding

Code Word Duration

Classic KEELOQ® Encoder

Manchester

PWM

Ultimate KEELOQ® Encoder

Manchester

PWM

187TE 23.979 ms

201TE 23.979 ms

437TE 46.527 ms

629TE 46.527 ms

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