HCS515_11 Datasheet, PDF(13/38 Page) Microchip Technology – KEELOQ® Code Hopping Decoder stand-alone decoder

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HCS515_11 Datasheet, PDF (13/38 Pages) Microchip Technology – KEELOQ® Code Hopping Decoder stand-alone decoder

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HCS515

FIGURE 4-8:

LEARN STATUS MESSAGE AFTER FIRST TRANSMISSION

TACT

TCLL

TCLKL

TCLKH

CLK

TCLA

TCLH

Decoder

Data

TDHI

0 0 00 0 0 00

Command Request

Status Byte

FIGURE 4-9:

CLK

TCLA

LEARN STATUS MESSAGE AFTER SECOND TRANSMISSION

TACT

TCLL

TCLKL

TCLKH

TCLH

TDHI

Decoder

DATA

0 OVR RSLT 0

Communications Request

0 0 0 1 CNT0

Learn Status Bits

CNT3 TX0

TX3 RX0 RX1

RX62 RX63

Decoded TX

4.3 Stand-Alone Mode

The HCS515 decoder can also be used in stand-alone

applications. The HCS515 will activate the data line for

up to 500 ms if a valid transmission was received, and

this output can be used to drive a relay circuit. To acti-

vate learn or erase all commands, a button must be

connected to the CLK input. User feedback is indicated

on an LED connected to the S_DAT output line. If the

CLK line is pulled high, using the learn button, the LED

will switch on. After the CLK line is kept high for longer

than 2 seconds, the decoder will switch the LED line off,

indicating that learn will be entered if the button is

released. If the CLK line is kept high for another 6 sec-

onds, the decoder will activate an ERASE_ALL com-

mand.

Learn mode can be aborted by taking the clock line

high until the data line goes high (LED switches on).

During learn, the data line will give feedback to the user

and, therefore, must not be connected to the relay drive

circuitry.

Note:

The Repeat bit must be cleared in the

configuration byte in Stand-alone

mode.

After taking the clock low and before a transmitter is

learned, any low-to-high change on the clock line may

terminate learn. This has learn implications when a

switch with contact bounce is used.

CII

4.4 Erase All Command and Erase

Command

The Table 4-3 describes two versions of the Erase All

command.

TABLE 4-3: ERASE ALL COMMAND

Command Subcommand

Byte

Description

C3 HEX

00 HEX

01 HEX

Erase all

transmitters.

Erase all transmit-

ters except 1. The

first transmitter in

memory is not

erased.

Subcommand 01 can be used where a transmitter with

permanent status is implemented in the microcontroller

software. Use of subcommand 01 ensures that the

permanent transmitter remains in memory even when

all other transmitters are erased. The first transmitter

learned after any of the following events is the first

transmitter in memory and becomes the permanent

transmitter:

1. Programming of the manufacturerâs code.

2. Erasing of all transmitters

(subcommand 00 only).

DS40183E-page 13

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