A20 User Manual (Revision 1.2) Copyright © 2013 Allwinner Technology Co., Ltd. All Rights Reserved. Page 642 / 812
6.6. IR
6.6.1. Overview
The CIR (Consumer IR) interface is used for remote control through infra-red light.
The CIR receiver samples the input signal on the programmable frequency and records these
samples into RX FIFO when one CIR signal is found on the air. The CIR receiver uses Run-Length
Code (RLC) to encode pulse width. The encoded data is buffered in a 64 levels and 8-bit width RX
FIFO; the MSB bit is used to record the polarity of the receiving CIR signal. The high level is
represented as ‘1’ while the low level is represented as ‘0’. The rest 7 bits are used for the length of
RLC. The maximum length is 128. If the duration of one level (high or low level) is more than 128,
another byte is used.
Since there is always some noise in the air, a threshold can be set to filter the noise to reduce system
loading and improve system stability.
The CIR interface features:
Full physical layer implementation
Support CIR for remote control
Support 64x8bits FIFO for data buffer
Programmable FIFO thresholds
Support Interrupt and DMA
6.6.2. IR Register List
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