DATA SHEET
MAS 35x9F
2.10.MP3 Block Input Mode
Table 2–3: MP3 bit rate vs. number of interrupts
A new so-called MP3 block input mode is now avail-
able which improves the input timing behavior of the
MAS 35x9F MPEG 1/2/2.5 Layer 3 decoder. The fol-
lowing sections provide a detailed description of this
new mode.
Bit Rate
[kbit/s]
Number of Interrupts
[1/s]
20
16
14
12
10
8
320
256
224
192
160
128
112
96
2.10.1.Functional Description of the MP3 Block
Input Mode
In MP3 block input, the MAS 35x9F generates a
demand for new input data each time one of its two
input buffers becomes available. The controller then
has to send one block of input data via the serial inter-
face SDIB. The block size is 2048 byte. The demand is
signalized via a pulse on the EOD pin.
7
Fig. 2–13 shows that the number of interrupts per sec-
ond does not depend on the data rate at the serial
interface. The maximum input data bit clock rate sup-
ported by the MAS 35x9F for all MPEG audio sampling
rates is 1.4 MHz.
6
80
5
64
4
Table 2–3 shows the average number of interrupts per
second for several typical MP3 bit rates.
The time period between two interrupts may vary
slightly even for fixed bit rate input streams due to the
MP3 specific bit reservoir.
Interrupt
Interrupt
a) SIC
b) SIC
Data blocks in a) and b) contain the same number of bytes.
t
Data block a) is sent with a lower data rate than data block b).
Fig. 2–13: Data Block Timing Diagram
Micronas
June 30, 2004; 6251-505-1DS
17
MICRONAS [ MICRONAS ]
