PCF5083HSLASHF2 datasheet(47/136 Pages) PHILIPS

47 / 136 page

1996 Oct 29

Philips Semiconductors

Objective speciﬁcation

GSM signal processing IC

PCF5083

9.1.4

AUDIO INTERFACE

9.1.4.1

Downlink speech frame format

Every 20 ms the speech decoder in the DSP outputs a speech frame consisting of 160 16-bit words. These speech

frames are transmitted to the PCM codec. The speech frame format is described in Table 32.

Table 31 Field descriptions

Table 32 Downlink speech frame format

FIELD

DESCRIPTION

SAMPLE

This ﬁeld contains the 13-bit linear PCM audio samples in two’s complement (MSB = sign bit)

representation as deﬁned by the

“GSM recommendation 06.01”.

PARM

Whenever the speech decoder is active the PARM ﬁeld is used to transfer the speech parameters

(D1 to D260) together with some frame classiﬁcation information (see Table 99) and the currently

selected test mode (see Table 34) out of the DSP. The terms SP (speech ﬂag), SID (silence descriptor)

and MUF (muting ﬂag) are deﬁned in

“GSM Rec. 06.31” (DTX for full-rate speech TCH). The HF bit

indicates, whether the speech codec is operating in handsfree mode (HF = 1) or not. The bits TM2 to TM0

are intended to be evaluated by an external Digital Audio Interface (DAI). They determine the currently

selected test mode during type approval as described in

“GSM Rec. 11.10, Section III.1.2.4.7”.

TM2 to TM0 are passed in the TMODE ﬁle of the operation_mode parameter of the speech decoder

procedure. Refer to Section 9.3.1 for more information.

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.

OFFSET

SAMPLE FIELD

PARM FIELD

SYNC FIELD

audio sample 0

TM1

TM0

audio sample 1

TM2

audio sample 2

3 to 27

audio samples 3 to 27

not used

audio sample 28

SID

audio sample 29

MUF

audio sample 30

audio sample 31

32 to 157

audio samples 32 to 157

158

audio sample 158

D258

D257

159

audio sample 159

D260

D259

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