SAA2520 Datasheet, PDF (21/36 Pages) NXP Semiconductors – Stereo filter and codec for MPEG layer 1 audio applications

Philips Semiconductors
Stereo filter and codec for MPEG layer 1
audio applications
Preliminary specification
SAA2520
Microcontroller interface
The SAA2520 has an interface connection to the serial interface of a microcontroller. The following signals are used:
LTCLK
LTDATA
LTCNT0
LTCNT1
LTENA
input
bi-directional
input
input
input
bit clock
serial data
control line 0
control line 1
enable
The SAA2520 microcontroller interface is enabled only if
LTENA (pin 34) is logic 1. Information to or from the
SAA2520 is conveyed in serial 8 or 16-bit units, whilst the
type of information is controlled by LTCNT0 (pin 35) and
LTCNT1 (pin 36).
A transfer commences when the microcontroller sets the
control lines to the correct combination for the required
action. LTENA is set to logic 1. The SAA2520 determines
its required action and prepares to transfer data. When the
microcontroller supplies the LTCLK, data is transferred to
or from the SAA2520 in units of 8-bits. 16-bit transfers are
conveyed as two 8-bit units during which LTENA remains
high.
During the transfer of 8-bit units, the least significant bit is
first to be transferred. When 16-bit units are transferred the
most significant byte is sent first.
EXTENDED SETTINGS (LTCNT1 = 0, LTCNT0 = 0)
Four information bits together with four address bits are
transferred in this mode. The order in which the bits appear
on the interface is:
D0..D1..D2..D3..A0..A1..A2..A3
Table 4 Extended Settings.
BIT
BIT
BIT
BIT
A3
A2
A1
A0
DESCRIPTION
0
0
0
0
CODEC external settings (see Table 5)
0
0
0
1
FILTER settings (see note 1)
0
0
1
0
not used
..
..
..
..
..
1
1
1
1
not used
Table 5 Extended Settings.
BIT
D0
D1
D2
D3
DESIGNATION
DEFAULT
MUTEDAC
1
ATTDAC
0
DEEMDAC
0
HOLDCLKOK
0
FUNCTION
connected to DAC mute input
connected to DAC attenuation input
emphasis control for DAC circuit
selects CLKOK hold mode
Note
If not used for DAC control, the MUTEDAC, ATTDAC and DEEMDAC can be used as general purpose output expanders.
August 1993
21