MCS3122

DS40001762A-page 14

 2014 Microchip Technology Inc.

5.7

Crystal Selection

Once the frequency band has been selected, the choice

of crystal frequency is flexible provided the crystal

meets the specifications summarized in Table 5-6, the

boundaries of the Encoder Frequency Configuration

value are followed and the RF transmit frequency error

is acceptable to the system design.

5.8

Seed Button Configuration

The MCS3122 allows the user to select which button

combination will output the seed transmission instead

of the normal data packet. Table 5-7 lists all the

possible button combinations.

5.9

Code Word Completion

MCS3122 always ensures that a full and complete

code word is transmitted even if all buttons are

released before transmission is complete.

5.10

Maximum Code Words

This feature sets a maximum number of code words

transmitted by a button configuration. If a button is kept

pressed, the maximum allowed code words will be

transmitted. If a new button is pressed or a new button

press combination is used, the process will be restarted

and the maximum number of words will be transmitted.

TABLE 5-6:

CRYSTAL RESONATOR SPECIFICATIONS

Symbol

Description

Min.

Typ.

Max.

Unit

Crystal Frequency

—

—MHz

Load Capacitance

—

15

—

pF

ESR

Equivalent Series Resistance

—

—

100

Ω

Note 1:

When selecting the 315.000 MHz frequency, a 24 MHz crystal is required.

TABLE 5-7:

SEED BUTTON

CONFIGURATION OPTIONS

SW2

SW1

SW0

Bit Settings

<3> and

<1:0>

Closed

Closed

Closed

000

Closed

Closed

Open

001

Closed

Open

Closed

010

Closed

Open

Open

011

Open

Closed

Closed

100

Open

Closed

Open

101

Open

Open

Closed

110

Open

Open

Open

Note 1:

The button combination corresponding to

the setting ‘111’ will not generate a seed

combination since it corresponds to all

buttons not pressed. Setting the bits to

this value will disable the seed packet

sending (i.e., no button combination will

send a seed code).