Preliminary
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Architecture
19.2.4.3 FIR Mode
In fast infrared mode (FIR), data transfer takes place between LH and peripheral devices at 4 Mbits/s
speed. A FIR transmit frame starts with preamble, followed by a start flag, frame data, CRC-32 and
ends with a stop flag.
shows the FIR transmit frame format.
Table 19-3. FIR Transmit Frame Format
Preamble
Start flag
Frame data
CRC-32
Stop flag
(16x)
On transmit, the FIR transmit state machine attaches the preamble, start flag, CRC-32, and stop flag. It
also encodes the transmit data into 4PPM format. It also generates the serial infrared interaction pulse
(SIP).
On receive, the FIR receive state machine recovers the receive clock, removes start flag, decodes the
4PPM incoming data and determines frame boundary with reception of stop flag. It also checks for
errors such as: illegal symbol, CRC error and frame-length error. At the end of a frame reception, the
LH reads the line status register (LSR) to find out possible errors of the received frame.
Data can be transferred both ways by the module but when the device is transmitting, the IR RX
circuitry is automatically disabled by hardware. Refer to the DISIRRX bit of the auxiliary control register
(ACREG[5]) for a description of the logical operation.
NOTE:
This applies to all three modes SIR, MIR, and FIR.
19.2.5 CIR Mode
In consumer infrared (CIR) mode, the infrared operation is designed to function as a programmable
(universal) remote control. By setting the MDR1 register, the UART can be set to CIR mode in the
same way as the other IrDA modes are set using the MDR1 register. The CIR mode uses a variable
pulse width modulation technique (based on multiples of a programmable T period) to encompass the
various formats of infrared encoding for remote control applications. The CIR logic is to transmit and
receive data packets according to the user definable frame structure and packet content.
19.2.5.1 Consumer IR Encoding
There are two distinct methods of encoding for remote control applications. The first uses time
extended bit forms, that is, a variable pulse distance (or duration) whereby the difference between a
logic 1 and logic 0 is the length of the pulse width; and the second is the use of a bi-phase where the
encoding of the logic 0 and logic 1 is in the change of signal level from 1 -> 0 or 0 -> 1, respectively.
Japanese manufacturers tend to favor the use of pulse duration encoding whereas European
manufacturers favor the use of bi-phase encoding.
The CIR mode is designed to use a completely flexible free format encoding where a digit ‘1’ from the
TX/RX FIFO is to be transmitted/received as a modulated pulse with duration T. Equally, a ‘0’ is to be
transmitted/received as a blank duration T. The protocol of the data is to be constructed and
deciphered by the host CPU. For example, the RC-5 protocol (
) using Manchester
encoding can be emulated as using a “01” pair for one and “10” pair for a zero.
1695
SPRUGX9 – 15 April 2011
UART/IrDA/CIR Module
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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