Start flag
Frame data
CRC-16
Stop flag
FIFO data
..............01111111111110........................................................
Start flags
xn
Bit-stuffing
.............0111110111110110........................................................
5x1
5x1
uart-010
Preliminary
Architecture
www.ti.com
19.2.4.2 MIR Mode
In medium infrared (MIR) mode, data transfer takes place between LH and peripheral devices at 0.576
or 1.152 Mbits/s speed. A MIR transmit frame starts with start flags (at least two), followed by a frame
data, CRC-16 and ends with a stop flag (see
).
Figure 19-8. MIR Transmit Frame Format
On transmit, the MIR state machine attaches start flags, CRC-16, and stop flags. It also looks for 5
consecutive 1s in the frame data and automatically inserts 0 after 5 consecutive 1s (this is called bit
stuffing).
On receive, the MIR receive state machine recovers the receive clock, removes the start flags, de-stuffs
the incoming data and determines frame boundary with reception of the stop flag. It also checks for
errors such as: frame abort, CRC error or frame-length error. At the end of a frame reception, the LH
reads the line status register (LSR) to find out possible errors of 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.
19.2.4.2.1 MIR Encoder/Decoder
To meet the MIR baud rate tolerance of +/–0.1 percent with a 48-MHz clock input, a 42-41-42
encoding/decoding adjustment is performed. The reference start point is the first start flag, and the
42-41-42 cyclic pattern is repeated until the stop flag is sent or detected.
The jitter created this way is within MIR tolerances. The pulse width is not exactly 1/4, but it is within the
tolerances defined by the IrDA specifications.
shows the MIR baud rate adjustment mechanism.
1692
UART/IrDA/CIR Module
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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