HCS101

DS41115D-page 6

Preliminary

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4.3.4

MINIMUM FOUR TRANSMISSIONS

(MTX4)

If this bit is cleared, at least one code word is completed

when the HCS101 is activated. If this bit is set, at least

four complete code words are transmitted.

4.3.5

TRANSMIT PULSE ENABLE (TXEN)

If this bit is cleared, no start pulse occurs before a

transmitted before the first code word’s preamble.

4.3.6

S3 SETTING (S3SET)

This bit determines the value of S3 in the function code

during a transmission and the high trip point selected

rors S2 during a transmission. If the S3SET bit is set,

S3 in the function code is always set, independent of

the value of S2.

4.3.7

EXTENDED SERIAL NUMBER

(XSER)

If this bit is cleared, the most significant four bits of the

32-bit Serial Number 1 are replaced with the function

code. If this bit is set, the full 32-bit Serial Number 1 is

transmitted.

5.0

SPECIAL FEATURES

5.1

Code Word Completion

Code word completion is an automatic feature that

ensures the entire code word is transmitted, even if the

button is released before the transmission is complete.

If the button is held down beyond the time for one code

word, multiple code words will result. If another button

is activated during a transmission, the active transmis-

sion will be aborted and a new transmission will begin

using the new button information.

5.2

Blank Alternate Code Word

Federal Communications Commission (FCC) Rules,

Part 15 specify the limits on fundamental power and har-

monics that can be transmitted. Power is calculated on

the worst case average power transmitted in a 100 ms

window. It is therefore advantageous to minimize the

duty cycle of the transmission by minimizing the duty

cycle of the individual bits and by blanking out consecu-

tive words. The transmission duty cycle can be lowered

by setting BRS. This reduces the average power trans-

mitted and hence, assists in FCC approval of a transmit-

ter device. Shortening the code word length and

transmitting only every other code word (Figure 5-1) also

may allow a higher amplitude transmission for greater

range.

5.3

Auto-Shutoff

The auto-shutoff function automatically stops the

device from transmitting if a button inadvertently gets

will prevent the device from draining the battery if a but-

ton gets pressed while the transmitter is in a pocket or

purse.

5.4

be transmitted as a one if the operating voltage has

dropped below the low voltage trip point. Refer to

Figure 3-2. The trip point is selectable based on the

battery voltage being used. See Section 4.3.2 for a

description of how the low voltage select option is set.

FIGURE 5-1:

CODE WORD TRANSMISSIONS

One Code Word

BRS = 0

BRS = 1

A

2A

100ms

100ms

100ms

100ms

Amplitude

Time