PDSP16510GCPR datasheet(20/25 Pages) MITEL

20 / 25 page

PDSP16510

(4) OUTPUT SCENARIOS

Considering the above sequence, therefore, some single

device situations can now be explained :

(4.1)

DOS is continuously present, but DEN is inactive

(Transform size less than 1024)

In this case, when the transform is complete, as the

device is programmed as a single device and DEN is

inactive, DAV will be made active. Even though DOS

is running, the status of DAV at this point does not rely

on it.

The user can now monitor the status of DAV, and after

at least 6 SCLK cycles can initiate some further action,

eg by external control force DEN active at some later

time when the rest of the system is ready to accept the

transformed data. Independently of this external

control, the next DOS pulse will start to operate the

sequence of events as described above (ie point No.

3.3). When DEN is eventually made active, the

remainder of the above sequence (points Nos 3.4 to

3.7) is executed, with 4 DEN-Enabled DOS pulses

needed before data is observed on the output pins.

If however the user immediately forces DEN active

upon monitoring DAV go active and waiting for the

required 6 SCLK cycles, then 5 DOS pulses would

have to be issued. The first of these 5 would start the

sequence of events as described above (3.3), and the

fact that it is enabled by DEN would be irrelevant. The

required DEN enabled pulses in this situation would be

the 2nd, 3rd, 4th and 5th pulses supplied.

(4.2)

DOS is not running, and DEN is inactive. (Transform

sizes less than 1024)

In this situation, again as the device is programmed to

be a single device and DEN is inactive at the point

where the transform is complete, DAV will be made

active regardless of the state of DOS. The user can

now monitor this event on DAV and after waiting a

further 6 SCLK cycles, use it to switch on DOS and to

make DEN active.

DOS can now be switched on for at least one pulse (but

may be more), and the sequence of events as

described earlier (from point No 3.3) will start. DEN can

then be made active, whereby a further 4 DEN-

Enabled DOS pulses will be required before data is

seen on the output pins. This is the situation shown in

table 3.

Alternatively, DEN and DOS could be made to operate

on the same cycle. In this case data will appear on the

output pins on the 5th DOS pulse (the first would not

actually require the presence of DEN, but the 2nd, 3rd,

4th and 5th would)

(4.3)

1024 point transforms, single device mode.

In the case of 1024 point transforms, the internal RAM

is no longer operated in the manner described in

section 2. The RAM is instead totally dedicated to one

operation at a time. Thus data for a transform will be

loaded, and all 12 out of 12 SCLK cycles will be

available for the transfer of input data to the RAMs.

During the transfrom no transfers from the input to the

RAM or from the RAM to the output are possible. This

is why DIS and DOS can be equal to SCLK for 1024

point transforms.

If 1024 point transforms are being performed and the

device is programmed as a single device, then

"asynchronous" operation of DAV is possible as

described earlier for transform sizes less than 1024

points. If DEN is inactive at the time the transform has

finished calculating, then DAV will be made to go active

regardless of the state of DOS. Although 6 SCLK

cycles do not have to be waited for as in section 3.2, a

transition has to be made from the transform

controlling the internal RAM to the output circuits

cnotrolling it. This operation plus the time taken to

advance data from the RAMs to the output buffer takes

exactly 4 SCLK cycles.

Hence the sequence of events is exactly as described

in section 3, except that section 3.3 should read 4

SCLK cycles rather than 6. The analysis of sections 4.1

and 4.2 are also true if the 6 SCLK cycle time is

substituted with 4 SCLK cycles.

(5) DUMMY DOS STROBES AFTER DEF

In addition to the dummy DOS strobes needed prior to

dumping data, it is necessary to provide at least 4 DOS strobes

after DEF has gone inactive, but before DAV goes active.

These initialise the internal address counters and do not rely

on DEN also being active. They are needed every time DEF

has been used to change the operating mode.

PDSP16510GCPR Datasheet(PDF) 20 Page - Mitel Networks Corporation

PDSP16510GCPR Datasheet(HTML) 20 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

Datasheet Download

Link URL