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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

 

 

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RDF

TDE

ROE

TUE

RFS

TFS

 

IF1

IF0

SSI STATUS REGISTER (SSISR)

X:$FFEE

 

 

 

 

 

(READ)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INPUT FLAGS

 

 

RECEIVE CLOCK

 

 

 

 

 

 

 

 

RECEIVE DATA

B7

B6

B5

B4

B3

B2

B1

B0

INPUT FLAG

 

 

 

 

 

 

 

 

 

 

SAMPLE

 

 

 

 

 

 

Figure 6-90 Input Flags

6.4.9Example Circuits

The DSP-to-DSP serial network shown in Figure 6-91 uses no additional logic chips for the network connection. All serial data is synchronized to the data source (all serial clocks and serial syncs are common). This basic configuration is useful for decimation and data reduction when more processing power is needed than one DSP can provide. Cascading DSPs in this manner is useful in several network topologies including star and ring networks.

DSP56002

 

 

DSP56002

 

DSP56002

 

DSP56002

DATA

 

 

 

 

 

 

DATA

IN

 

 

 

 

 

 

OUT

SRD

STD

SRD

STD

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

SC2

SERIAL CLOCK

 

 

 

 

 

 

 

SERIAL SYNC

 

 

 

 

 

 

 

Figure 6-91 SSI Cascaded Multi-DSP System

MOTOROLA PORT C 6 - 157

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

TDM networks are useful to reduce the wiring needed for connecting multiple processors. A TDM parallel topology, such as the one shown in Figure 6-92, is useful for interpolating filters. Serial data can be received simultaneously by all DSPs, processing can occur in parallel, and the results are then multiplexed to a single serial data out line. This configuration can be cascaded and/or looped back on itself as needed to fit a particular application (see Figure 6-93). The serial and parallel configurations can be combined to form the array processor shown in Figure 6-94. A nearest neighbor array, which is applicable to matrix relaxation processing, is shown in Figure 6-95. To simplify the drawing, only the center DSP is connected in this illustration. In use, all DSPs would have four three-state buffers connected to their STD pin. The flags (SC0 and SC1) on the control master operate the three-state buffers, which control the direction that data is transferred in the matrix

(north, south, east, or west).

The bus architecture shown in Figure 6-96 allows data to be transferred between any two DSPs. However, the bus must be arbitrated by hardware or a software protocol to prevent collisions. The master/slave configuration shown in Figure 6-97 also allows data to be transferred between any two DSPs but simplifies network control.

6 - 158 PORT C MOTOROLA

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

DSP56002

SRD

STD

SCK

SC2

 

DSP56002

 

SRD

STD

 

 

SCK

 

SERIAL

SC2

SERIAL

DATA IN

DATA OUT

 

DSP56002

SRD

STD

SCK

SC2

DSP56002

SRD STD

SCK

SC2

SERIAL SYNC

SERIAL CLOCK

Figure 6-92 SSI TDM Parallel DSP Network

MOTOROLA PORT C 6 - 159

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

 

 

DSP56002

 

DSP56002

 

SRD

STD

SRD

STD

 

 

SCK

 

SCK

 

 

SC2

 

SC2

Inc.

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

 

 

 

 

Semiconductor,

 

SCK

 

SCK

 

SC2

 

SC2

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SC2

 

SC2

Freescale

 

 

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

 

 

 

 

 

 

SCK

 

SCK

 

 

SC2

 

SC2

SERIAL CLOCK

FRAME SYNC

Figure 6-93 SSI TDM Connected Parallel Processing Array

6 - 160 PORT C MOTOROLA

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

 

DSP56002

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

DSP56002

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

SERIAL

 

 

 

 

SERIAL

IN

 

 

 

 

OUT

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

DSP56002

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

DSP56002

 

DSP56002

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

 

SERIAL CLOCK

 

 

 

 

SERIAL SYNC

 

 

Figure 6-94 SSI TDM Serial/Parallel Processing Array

MOTOROLA PORT C 6 - 161

For More Information On This Product, Go to: www.freescale.com

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

SYNCHRONOUS SERIAL INTERFACE (SSI)

 

DSP56002

DSP56002

 

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

SC0

SCK

 

SCK

 

SCK

SC1

SC2

 

SC2

 

SC2

 

DSP56002

DSP56002

 

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

DSP56002

DSP56002

 

 

DSP56002

SRD

STD

SRD

STD

SRD

STD

 

SCK

 

SCK

 

SCK

 

SC2

 

SC2

 

SC2

 

 

SERIAL CLOCK

 

 

 

 

 

FRAME SYNC

 

 

 

Figure 6-95 SSI Parallel Processing — Nearest Neighbor Array

6 - 162 PORT C MOTOROLA

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