saa7327 NXP Semiconductors, saa7327 Datasheet - Page 17

• Manufacturer Part Number: saa7327
• Description: Digital Servo Processor And Compact Disc Decoder With Integrated Dac For Video Cd Cd7 Ii
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.8
7.8.1
The onboard bitstream DAC operates at a clock frequency
of 96f
1f
circuit used and careful consideration should be given to
the recommended application circuits shown in
Figs 38 and 39. The onboard DAC is controlled from
shadow register 7 (see Section 7.15.3 for definition of
shadow registers). This shadow register controls routing of
data into the onboard DAC and also controls the DAC
output pins, which can be held at zero when the onboard
DAC is not required; see Table 4.
Audio data from the decoder part of SAA7327 can be
routed as described in Sections 7.8.1.1 and 7.8.1.2.
7.8.1.1
Setting shadow register 7 to XX11 will route audio data
from the CD7 II decoder into the internal DAC and enables
the DAC output pins (LN, LP, RN, RP). To enable the
on-board DAC, the DAC interface format (set by register 3)
must be set to 16-bit 1fs mode, either I
CD-ROM mode can also be used if interpolation is not
required. The serial data output pins for interfacing with an
external DAC (SCLK, WCLK, DATA and EF) are set to
high-impedance.
Table 4 Shadow register
2000 Jun 26
s
Digital servo processor and Compact Disc
decoder with integrated DAC for video CD (CD7 II)
. Optimum performance is dependent on the application
SHADEN
s
and is designed for operation with an audio input at
DAC interface
1
I
C
NTERNAL BITSTREAM
ONVERTER
Use onboard DAC
ADDRESS
SHADOW
0111 (7H)
(DAC)
D
IGITAL
control of
onboard DAC
REGISTER
-
TO
2
S or EIAJ format.
-A
NALOG
DATA
XXX0
XXX1
XX0X
XX1X
17
7.8.1.2
The onboard DAC can also be set to accept digital audio
inputs from an external source, e.g. audio from a VCD
decoder IC. This is known as loopback mode and is
enabled by setting shadow register 7 to XX01. This
enables the serial data output pins SCLK, WCLK, DATA
and EF so that data can be routed to the external VCD
decoder (or external DAC).
The digital audio data output from the VCD decoder can
then also be input to the onboard DAC on the SAA7327 by
utilising the serial data input interface (SCLI, SDI and
WCLI).
In this mode, a wide range of data formats to the external
VCD IC can be programmed as shown in Table 4.
However, the serial inputs on the SAA7327 will always
expect the input digital audio data from the VCD IC to be
16-bit 1f
EIAJ, as the serial output format (set by decoder
register 3). In fact, the onboard DAC will also accept 18-bit
I
and the 2 LSBs discarded.
2
S-bus data; in this case the 16 MSBs only will be read
hold onboard DAC outputs at
zero
enable onboard DAC outputs
use external DAC or route audio
data into onboard DAC
(loopback mode)
route audio data into onboard
DAC (non-loopback mode)
s
and the same data format, either I
Loopback external data into onboard DAC
FUNCTION
Product specification
SAA7327
2
S-bus or
RESET
reset
reset