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CIRCC

Consumer Infrared Communications Controller

SMSC -> Microchip 

CONSUMER IR (REMOTE CONTROL)

INTRODUCTION

NEC HARDWARE FRAME DECODING

The CIrCC Consumer IR Remote Control block

is a general-purpose programmable

Synchronous Amplitude Shift Keyed serial

communications interface that includes a Carrier

Frequency Divider, a Programmable Receive

Carrier Range Sensitivity Register, Receive and

Transmit Modulators and an NEC PPM Frame

Format Decoder.

The Consumer IR transmit block transfers data

LSB first between the SCE and Output

Multiplexer as a fixed bit-cell serial NRZ data

stream. The components of this block can also

modulate serial data at programmable data rates

and carrier frequencies.

Variable length encoding and message framing

is handled during transmit by system software.

Receive message framing may be handled by

either hardware or software. The high degree of

control afforded to the system software allows for

the support of many encoding methods; including

PPM, PWM and RC-5 Remote Control formats.

General

The CIrCC implements hardware-level decoding

for the NEC Consumer IR Remote Control

format. The hardware decoder may be used to

generate a wake-up event or to send parts of the

received message frame to the FIFO. The No

Care Custom Code (NCCC), No Care Data Code

(NCDC), PME Wake and Frame bits of the

Consumer IR Control register configure the

hardware decoder.

NEC Consumer IR Format

The NEC Consumer IR Remote Control format

specifies a 38kHz carrier, 13ms of sync framing,

and 32 bits of pulse-position modulated (PPM)

message data. The message data includes an 8

bit Custom Code field, an 8 bit Custom Code’

field, an 8 bit Data Code field, and an 8 bit Data

Code’ field. A single frame of the NEC PPM

Consumer Remote Control output is shown in

Figure 5.

Register controls for the Consumer IR hardware

can be found in Register Block Two. They are

the Consumer IR Control Register, the

Consumer IR Carrier Rate Register, the

Consumer IR Bit Rate Register, the Custom

Code Register, the Custom Code’ Register, and

the Data Code Register.

The Custom Code fields in this protocol uniquely

address message frames for specific devices.

The Custom Code fields can be used as a 16 bit

address or as an 8 bit address followed by the

bit-wise complement of the Custom Code field

Custom Code’. The Data Code field is an 8 bit

command code, Data Code’ is the bit-wise

complement of Data Code.

Note: The CIrCC hardware can decode NEC

protocol framing (sync pulse, 32 bit PPM

message data) at any carrier frequency or data

rate, depending on the programmed Carrier

Frequency Divider (CFD) and Bit Rate Divider

(BRD).

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