MAS3506D datasheet(8/52 Pages) MICRONAS

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MAS 3506D

PRELIMINARY DATA SHEET

Micronas

2.2.1.1. Broadcast Channel Timing

The incoming Broadcast Channel bitstream has a

framing with a period between Prime Rate Channel

Preambles (PRCP) of

prcpt = 432 ms

During one frame the transmission of the BC is inter-

rupted by a gap prcpgap of:

prcpgap = 2.5 ms

The data transmission is interrupted by a second gap

mfpgap with a duration of

mfpgap = 1.2 ms

that is synchronous with the Master Frame Preamble

(MFP) cycle with a period of:

mfpt = 138 ms

Both cycles mfpt and prcpt have a least common multi-

ple at 9936 ms. These gaps are independent of the

number of Prime Rate Channels (PRC) n that create

the considered Broadcast Channel.

2.2.1.2. Buffer-Controlled Loop

For the recovery of the audio sample clock, a buffer-

controlled loop is used that operates on the incoming

Broadcast Channel bit stream. The buffer control loop

characteristic suppresses the effects of these gaps on

the stability of the generated audio sample frequency

by more than 40 dB. Thus, no audible jitter is intro-

duced to the derived reference clock for the D/A con-

verter (see section 2.3. "Clock Management").

The step response of the buffer-controlled loop is plot-

ted in Figure 2–2 with respect to different number of

PRCs. The settling time for the buffer-controlled loop is

about 10 s.

Fig. 2–2: buffer-controlled loop step response

2.2.2. Broadcast Channel Demultiplexing

The Service Control Header that directly follows the

SCH-preamble in the BC bitstream is made accessible

to the controller after it has been detected. Its availabil-

ity is indicated by the BC-FRAME-SYNC signal. Infor-

mation about the content of the Broadcast Channel is

given in the Service Control Header data. The control-

ler may select the number of the Service Component

that is to be passed to the internal MPEG audio

decoder. By default, always Service Component “0” is

decoded

the

MAS 3506D.

implemented

autoscan mode can be selected that skips non-audio

Service Components.

2.2.3. MPEG Audio Decoding

The MPEG 1/2/2.5 Layer 3 decoder performs the

audio decoding. The steps for decoding are:

– Synchronization

– Side information extraction

– Huffman decoding

– Synthesis filter bank

– Ancillary data extraction

The bit rates and sampling rates that are supported by

the MAS 3506D are listed in Table 2–1.

Frame synchronization and decoding error signals are

provided at output pins of the MAS 3506D.

2.2.4. Baseband Processing

A digital volume control matrix is applied to the digital

stereo audio data. This matrix may also perform addi-

tional balance control and a simple kind of stereo

basewidth enhancement. The four factors LL, LR, RL,

and, RR are adjustable via the controller with 20 bit

resolution (see Fig. 3–2 on page 28).

4.3

8.6

0.02

0.04

0.06

0.08

0.1

0.12

t/s

Table 2–1: Sampling frequencies and bit rates

Sampling Freq. in kHz

Bit rates in kBit/s

48, 32, 24, 16, 12, 8

128, 112, 96, 80, 64, 56,

48, 40, 32, 24, 16, 8

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