PDSP16515GCPR datasheet(16/27 Pages) MITEL

16 / 27 page

PDSP16515A

Figure 8. Three Device System with Separate Load, Transform, and Dump Operations

DUMP A1

DAV A

LFLG A

INEN B

LFLG B

DAV B

LOAD A1

LOAD A2

LOAD B1

LOAD B2

INEN A

DEF

DIS / DOS

INTERNAL

START

TRANSFORM A1

TRANSFORM B1

DUMP B1

TRANSFORM A2

In this operating mode the DIS and DOS strobes can often be

tied together, since a faster DOS strobe gives no improvement

in the sampling rates possible. This remains true even when

the output rate must be twice or four times the input rate due

to block overlapping. Options can then be used which

internally divide the DIS strobe by two or four, and thus allow

the input to be driven by the faster DOS strobe.

In this mode the LFLG goes in-active after 25%, 50%, or 100%

of the block has been loaded. When multiple transforms are

performed concurrently (for example 4 x 64) a LFLG transition

occurs at the relevant point whilst the first block in the group

is being loaded. LFLG then goes high again and returns low

at the overlap point in the last block. This double LFLG

transition allows two devices to support 50% block

overlapping, since the first transition from the first device can

be used to initiate the load procedure in the second device.

The second transition from the second device then initiates a

new load procedure in the first device. The additional edges

from each device have no effect since they occur when the

device they are driving is already doing a load operation.

In such a two device system supporting 50% overlaps the

inverted DAV from the first device must drive the DEN input of

the second device. The data dumping time is then shared

equally between both devices. The second device only

outputs data when the first has finished, but both dumps must

be finished in the time taken to load the group of blocks if only

one output processor is provided. Without the DAV/DEN

connection one device would only have had the time needed

to load half of one sub block in which to dump its data.

In a similar manner four devices will handle 75% overlaps

when concurrent multiple transforms are to be computed. The

second, third, and fourth devices make use of the first

transition, and ignore the second. The first device uses the

second transition from the last device, and ignores the first.

With the DAV/DEN connection each device will have one

quarter of the load time to dump its data when a single output

processor is provided .

More than two devices will provide increased performance for

multiple transforms with 50% overlapping, and more than four

devices will increase the performance with 75% overlapping.

External logic is then needed to ensure that each device only

uses the correct LFLG transition. Any device should only use

the negative LFLG transition from a previous device if its own

LFLG is low, and the LFLG output from the previous device

plus one is low.

Mode 2 (BITS 10:9 = 10)

This mode is suitable for all transform sizes, since separate

load, transform, and then dump operations occur. More

devices than required by Mode 1 are necessary to achieve a

given sampling rate, but the input and output rates can be any

value up to the full system clock rate. As with Mode 1,

additional output processors are needed

to avoid the

sampling rate restriction imposed by block overlapping.

PDSP16515GCPR Datasheet(PDF) 16 Page - Mitel Networks Corporation

PDSP16515GCPR Datasheet(HTML) 16 Page - Mitel Networks Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

Datasheet Download

Link URL