PCF5083 datasheet(51/136 Pages) PHILIPS

51 / 136 page

1996 Oct 29

Philips Semiconductors

Objective speciﬁcation

GSM signal processing IC

PCF5083

9.1.5.2

Format of downlink data frames

The downlink data frame format is described in Table 40. Each word consists of four ﬁelds; these are described in

Table 37.

Table 37 Field descriptions

Table 38 Classiﬁcation of the 16-bit samples

Table 39 Valid values for FID

Note

1. Binary value; X = don’t care.

FIELD

DESCRIPTION

DATA

Depending on the contents of the CMD ﬁeld (see Table 38), this ﬁeld contains a data byte belonging to a

user or a control data block or auxiliary control information for the terminal adaptor.

CMD

This ﬁeld classiﬁes the 16-bit samples as described in the Table 38.

SYNC

Synchronization signal for external (test) equipment. Marks the 20 ms speech frames. Each falling edge of

SYNC marks the beginning of a new output speech frame and with a constant offset due to internal

module processing time the rising edge of SYNC marks a new input speech frame. As soon as audio

output data are available this bit always reﬂects the internal speech frame timing independently of other

processing tasks of the DSP.

INFO

This ﬁeld may be used by external devices to distinguish between audio and data frames. The INFO ﬁeld

of word#2 contains the so called frame identiﬁcation (FID); see Table 39.

CMD FIELD

DESCRIPTION

76543

00001

The data ﬁeld contains a valid data byte belonging to either a user or a control data block.

00010

The data ﬁeld contains auxiliary control information that may be used by the terminal

adaptor for synchronization purposes.

11111

Indicates that the data ﬁeld contains invalid data, which should be ignored.

Other combinations

Reserved for future expansion. Not used by the DSP.

FID(1)

FRAME TYPE

audio frame

data frame

reserved

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