IRCC datasheet(13/79 Pages) SMSC

13 / 79 page

Receiver Bit Cell Synchronization

The

Consumer

Receiver

demodulates

incoming ASK waveforms into NRZ data for the

SCE.

The IrCC uses the edges of the

demodulated incoming infrared data to indicate

changes in bit state.

For continuous periods of high or low data

without transitions, the IrCC samples the signal

level in the center of each incoming bit period.

Using the Receiver Bit Cell Synchronization

mechanism, any transition resets the timer that is

used in the sampling process to eliminate errors

due to timing differences between the receive

decoder and the incoming bit period (Figure 6).

Receiver synchronization can be disabled to

allow direct sampling of the demodulated

incoming infrared data stream at some preset

receive bit rate. This is useful in situations where

the speed of the receive data is not strictly

known. In such cases, the receive bit rate is set

as high as possible, the

Receiver Bit Cell

Synchronization is disabled, and the system

software is used to measure the bit-cell period

from the oversampled data.

The learned

parameters can then be used to switch to the

synchronized, fixed bit-cell mode to reduce

processing overhead in the host CPU for all

future transactions.

Sync

IR Rx Data

NRZ Rx Data

(SYNC)

NRZ Rx Data

(No SYNC)

Clock

678

Clock

FIGURE 6 - TV REMOTE RECEIVER: SYNC VS. NO SYNC

IRCC Datasheet(PDF) 13 Page - SMSC Corporation

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