Texas Instruments TMS320C6457 Manual de usuario descargar pdf (Pagina 19)

MAP

decoder

unit

A for MAP 1

and A’ for MAP2

B for MAP1

and B’ for MAP2

(only rate 1/4)

X for MAP1

or X’ for MAP2

EXT

: extrinsics after MAP1

EXT

: extrinsics after MAP2

EXT

1,2

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Shared-Processing (SP) Mode

Figure 16. Shared-Processing (SP) Mode Block Diagram

The shared-processing mode allows the DSP/TCP2 system to support frames strictly larger than 20730.

The DSP breaks the large frame into 2 or more smaller frames of 20480 or less. Each frame is called a

subframe. The size of all the subframes (except the last subframe) must be divisible by 256. The DSP

breaks the large frame into several sub-frames following the process shown below. The first subframe

does not have a header section and its tail section is equal to the prolog size. The middle subframe

header and tail section sizes are each equal to the prolog size. The last subframe header size is equal to

the prolog size and the tail section is equal to the tail size. The prolog size must be integer divisible by 8.

The sub-frames reliability portions are sequenced in order to create the full frame.

1. The first subframe (required) will have a opmode of 1. The middle subframe(s) (optional) have a

opmode of 2. The last subframe (required) will have a opmode of 3.

2. The size of all the subframes (except the last subframe) must be integer divisible by 256 and Max sub

frame size = 20480 = 80*256.

3. The first and middle subframes should have the same size. The last subframe should be approximately

the same size as the other subframes.

4. The last subframe size must be at least 129.

SPRUGK1 – March 2009 TMS320C6457 Turbo-Decoder Coprocessor 2 19

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Texas Instruments TMS320C6457 Manual de usuario Pagina 19