Philips Semiconductors
Audio In
PRELIMINARY SPECIFICATION
8-3
clock system DDS is used to provide a single master A/
D and D/A clock. The AO unit, or the D/A converter, can
be used as serial interface timing master, and the AI unit
is set to be slave to the serial frame determined by
(AI SER_MASTER=0, AI_SCK and AI_WS externally
wired to the corresponding AO pins). In such systems, in-
dependent software control over A/D and D/A sampling
rate is not possible, but component count is minimized.
AO
8.5
SERIAL DATA FRAMING
The AI unit can accept data in a wide variety of serial
data framing conventions.
Figure 8-2
illustrates the no-
tion
of
a
serial
frame.
CLOCK_EDGE=0, a frame is defined with respect to the
positive transition of the AI_WS signal, as observed by a
positive clock transition on AI_SCK. Each data bit sam-
pled on positive AI_SCK transitions has a specific bit po-
sition: the data bit sampled on the clock edge after the
clock edge on which the AI_WS transition is seen has bit
position 0. Each subsequent clock edge defines a new
bit position. As defined in
Table 8-5
, other combinations
If
POLARITY=1
and
of POLARITY and CLOCK_EDGE can be used to define
a variety of serial frame bitposition definitions.
The capturing of samples is governed by FRAMEMODE.
If FRAMEMODE=00, every serial frame results in one
sample from the serial-parallel converter. A sample is de-
fined as a left/right pair in stereo modes or a single left
channel value in mono modes. If FRAMEMODE=1y, the
serial frame data bit in bit position VALIDPOS is exam-
ined. If it has value
‘
y
’
, a sample is taken from the data
stream (the valid bit is allowed to precede or follow the
left or right channel data provided it is in the same serial
frame as the data).
The left and right sample data can be in a LSB-first or
MSB-first form, at an arbitrary bit position, and with an ar-
bitrary length.
Table 8-3. Sample rate settings (f
DSPCPUCLK
=133
MHz, improved PNX1300 mode)
f
s
OSCLK
SCK
FREQUENCY
SCKDIV
44.1 kHz
256f
s
256f
s
384f
s
384f
s
64f
s
64f
s
64f
s
64f
s
2187991971
3
48.0 kHz
2191574340
3
44.1 kHz
2208246133
5
48.0 kHz
2213619686
5
Table 8-4.AI MMIO clock & interface control bits
Field Name
Description
SER_MASTER
0
(RESET default), the A/D converter
is the timing master over the serial inter-
face. AI_SCK and AI_WS are set to be
inputs.
1
PNX1300 is timing master over the
AI serial interface. The AI_SCK and
AI_WS pins are set to be outputs.
Sets the clock frequency emitted by the
AI_OSCLK output. RESET default 0.
Sets the divider used to derive AI_SCK
from AI_OSCLK. Set to 0..255, for divi-
sion by 1..256. RESET default 0.
Sets the divider used to derive AI_WS
from AI_SCK. Set to 0..511 for a serial
frame length of 1..512. RESET default 0.
FREQUENCY
SCKDIV
WSDIV
7
6
5
4
3
2
1
0
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
AI_SCK
AI_WS
frame
n
0
AI_SD
frame
n+1
Figure 8-2. AI serial frame and bit position definition (POLARITY=1, CLOCK_EDGE=0).
Table 8-5. AI MMIO serial framing control fields
Field Name
Description
POLARITY
0
serial frame starts on AI_WS negedge
(RESET default)
1
serial frame starts on AI_WS posedge
00
accept a sample every serial frame
(RESET default)
01
unused, reserved
10
accept sample if valid bit = 0
11
accept sample if valid bit = 1
Defines the bit position within a serial frame
where the valid bit is found.
Default 0.
Defines the bit position within a serial frame
where the first data bit of the left channel is
found.
Default 0.
Defines the bit position within a serial frame
where the first data bit of the right channel
is found.
Default 0.
0
MSB first (RESET default)
1
LSB first
Start/Stop bit position. Default 0.
If DATAMODE=MSB first, SSPOS deter-
mines the bit index (0..15) in the parallel
word of the last data bit. Bits 15 (MSB) up
to/including SSPOS are taken in order from
the serial frame data. All other bits are set
to
‘
0
’
.
If DATAMODE=LSB first, SSPOS deter-
mines the bit index (0..15) in the parallel
word of the first data bit. Bits SSPOS up to/
including 15 are taken in order from the
serial frame data. All other bits are set to
‘
0
’
.
FRAMEMODE
VALIDPOS
LEFTPOS
RIGHTPOS
DATAMODE
SSPOS