HCS500T-ISLASHST datasheet(13/42 Pages) MICROCHIP

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DS40000153E-page 13

HCS500

4.2.7

ACTIVATE LEARN

The activate Learn command (Figure 4-6) is used to

activate a transmitter learning sequence on the

decoder. The command consists of a Command mode

activation sequence, a command byte, and two dummy

bytes. The decoder will respond by taking the data line

high to acknowledge that the command was valid and

that learn is active.

Upon reception of the first transmission, the decoder

will respond with a learn status message (Figure 4-7).

During learn, the decoder will acknowledge the

reception of the first transmission by taking the data line

high for 60 ms. The controlling microcontroller can

clock out at most eight bits, which will all be zeros. All

of the bits of the status byte are zero, and this is used

to distinguish between a learn time-out status string

and the first transmission received string. The

controlling microcontroller must ensure that the clock

line does not go high 60 ms after the falling edge of the

data line, for this will terminate learn.

Upon reception of the second transmission, the

decoder will respond with a learn status message

(Figure 4-8).

The

learn

status

message

after

the

second

transmission consists of the following:

• 1 Start bit.

• The function code [S3:S0] of the message is zero,

indicating that this is a status string.

• The RESULT bit indicates the result of the learn

sequence. The RESULT bit is set if successful

and cleared otherwise.

• The OVR bit will indicate whether an exiting

transmitter is over written. The OVR bit will be set

if an existing transmitter is learned over.

• The [CNT3…CNT0] bits will indicate the number

of transmitters learned on the decoder.

• The [TX3…TX0] bits indicate the block number

used during the learning of the transmitter.

FIGURE 4-6:

LEARN MODE ACTIVATION

FIGURE 4-7:

LEARN STATUS MESSAGE AFTER FIRST TRANSMISSION

FIGURE 4-8:

LEARN STATUS MESSAGE AFTER SECOND TRANSMISSION

Decoder

MSB

Command Byte

Start Command

LSB

TLRN

Dummy Byte

CLK

C DATA

Acknowledge

MSB

LSB

MSB

LSB

TACK

TRESP

TACK2

DATA

Command Request

TCLKL

TCLKH

TCA

TDS

TCLL

TDHI

TCLA

TCLH

CLK

Decoder

Status Byte

Data

Communications Request

TCLKL

TCLKH

TCA

TDS

Cii

TCLL

TDHI

TCLA

TCLH

CLK

Decoder

TX0

TX3

RX63

OVR RSLT

CNT0

CNT3

RX0

RX1

RX62

Learn Status Bits

Decoded Tx

Data

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