PCF5083HSLASH001SLASHF2 datasheet(43/136 Pages) PHILIPS

43 / 136 page

1996 Oct 29

Philips Semiconductors

Objective speciﬁcation

GSM signal processing IC

PCF5083

DESCRIPTION OF THE DSP CORE

9.1

Interface description

9.1.1

BASEBAND DIGITIZER INTERFACE

The PCF5083 serial input port SIX is used for the reception

of off-air data from the baseband digitizer PCF5072 (BBD).

The port consists of:

• Serial Input Data signal (SIXD), containing 16I and 16Q

data bits, MSB first

• Serial Input Clock signal (SIXCLK), running at 13 MHz

• Serial Input Enable signal (SIXEN), active LOW.

Regularly spaced I and Q samples are sent to the DSP

with a periodicity of 1/(2 270.833 kHz); (twice the GSM bit

period). The number of incoming samples expected by the

DSP depends upon the current status in which the DSP is

operating (see Table 27).

The column START OF SAMPLING indicates in which

time slot (1 time slot = 1/8 TDMA frame = 577

µs) the

sampling of the I and Q pairs has to start.

Time slots are numbered from 0 to 7, whereby slot 0 is

defined as the receive time slot of the mobile station (see

Section 8.3.2.1).

Each I/Q component pair is represented by two 16-bit

two’s complement numbers, as shown in Table 28, with

one sign bit (I15 and Q15) and 15 fractional bits. The range

for the I and Q components is specified below.

Range:

−1.0 ≤ I,Q < +1.0

It should be noted that due to the limited SNR of the

PCF5072 of 66 dB, only the 11 MSBs of I and Q contain

meaningful data.

The I and Q components are defined as follows:

I = f(A)

× cos Φ

Q = f(A)

× sin Φ

where A is the magnitude and

Φ is the phase of the

antenna input signal. The function f(A) describes the

characteristic of the AGC applied (see Fig.16).

Table 27 Time window for BBD output data

Note

1. The value 1404 for FCB search is the default value after reset. It can be changed by the FB_search_fcb_init

procedure.

Table 28 I and Q component format

OPERATION STATUS

START OF SAMPLING

NUMBER OF I AND Q PAIRS

Reception of a normal burst

TS 0

149

Reception of a synchronization burst

−

167

Reception of a normal burst

TS 0

167

Level measurement of neighbouring BCCH

TS 5

DC offset measurement

TS 5

128

FCB search

TS 6

1404(1) (9

× 156)

BIT

I15

I14

I13

I12

I11

I10

O15

O14

O13

O12

O11

O10

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