MAS3507D Micronas Intermetall, MAS3507D Datasheet - Page 8

• Manufacturer Part Number: MAS3507D
• Description: Mpeg 1/2 Layer 2/3 Audio Decoder
• Manufacturer: Micronas Intermetall

MAS 3507D
2.3. Program Download Feature
This is an additional feature that is not required for the
MPEG decoding function.
The overall function of the MAS 3507D can be altered
by downloading up to 1 kWord program code into the
internal RAM and executing this code instead of the
ROM code. During this time, MPEG decoding is not
possible.
The code must be downloaded by the ‘write to mem-
ory’ command (see Section 3.3.) into an area of RAM
that is switchable from data memory to program mem-
ory. A ‘run’ command (see Section 3.3.1.) starts the
operation.
Micronas provides modules for voice-decoding using
the CELP algorithm (performing good speech quality
at very low bit rates) and for encoding and decoding
audio data with ADPCM.
Detailed information about downloading is provided in
combination with the MAS 3507D software develop-
ment package from Micronas.
For commercial issues and detailed information please
contact our sales department.
8
2.4. Baseband Processing
2.4.1. Volume Control / Channel Mixer
A digital volume control matrix is applied to the digital
stereo audio data. This performs additional balance
control and a simple kind of stereo basewidth
enhancement. The 4 factors LL, LR, RL, and RR are
adjustable via the controller with 20-bit resolution. See
Fig. 3–2 and Section 3.7.3. for details.
2.4.2. Mute / Bypass Tone Control
A special bit enables a fast and simple mute functional-
ity without changing the current volume setting.
Another bit allows to bypass the complete bass / treble
/ volume control. See for details Section 3.6.2.
2.4.3. Bass / Treble Control
Tone control is implemented in the MAS 3507D. It
allows the control of bass and treble in a range up to
±15 dB, as Table 3–9 shows. To prevent overflow or
clipping effects, the prescaler is built-in. The prescaler
decreases the overall gain of the tone filter, so the full
range up to +15 dB is usable without clipping.
Due to the different frequency ranges in MPEG 1,
MPEG 2, or MPEG 2.5, the bass cutoff frequencies dif-
fer.
Table 2–1: Cutoff Frequencies
For details see Section 3.6.3..
Cutoff
MPEG 1
MPEG 2
MPEG 2.5
Bass
100 Hz
200 Hz
400 Hz
PRELIMINARY DATA SHEET
Treble
10 kHz
10 kHz
10 kHz
Micronas