Philips Semiconductors
Audio Out
PRELIMINARY SPECIFICATION
9-5
Every serial frame transmits a single left and right chan-
nel sample, and optional codec control data to each D/A
converter. The left and right sample data can be in an
LSB first or MSB first form, at an arbitrary serial frame bit
position, and with an arbitrary length.
In MSB-first mode (DATAMODE = 0), the parallel to se-
rial converter sends the value of LEFT[MSB] in bit posi-
tion LEFTPOS in the serial frame. Subsequently, bits
from decreasing bit positions in the LEFT data word, up
to and including LEFT[SSPOS], are transmitted in order.
In LSB-first mode (DATAMODE = 1), the parallel-to-seri-
al converter sends the value of LEFT[SSPOS] in bit po-
sition LEFTPOS in the serial frame. Subsequent bits
from the LEFT data word, up to and including
LEFT[MSB], are transmitted in order.
Table 9-6
. shows
the transmitted bits in different modes.
Frame bits that do not belong to either LEFT[MSB:SS-
POS] or RIGHT[MSB:SSPOS] or a codec control field
(
Section 9.7,
“
Codec Control
”
) are shifted out as zero.
This zero extension ensures that PNX1300 can be used
in combination with D/A converters of higher precision
than the actual number of transmitted bits in the current
operating mode, e.g. 18-bit D/As operating with 16-bit
memory data.
9.6.1
Serial Frame Limitations
Due to the implementation, there is a minimum serial
frame length required that is operating mode dependent.
This is shown in
Table 9-7
.
Table 9-5. AO Serial Framing Control Fields
Field Name
Description
POLARITY
0
serial frame starts with an AO_WS
negedge (RESET default)
1
serial frame starts with an AO_WS
posedge
This bit should NOT be changed during
operation of the AO unit, i.e. only update this
bit when TRANS_ENABLE = 0.
Defines the bit position within a serial frame
where the first data bit of the left channel is
placed. Reset default
‘
0
’
.
Defines the bit position within a serial frame
where the first data bit of the right channel is
placed. Reset default
‘
0
’
.
0
MSB first (RESET default)
1
LSB first
Start/Stop bit position. Reset default 0. Note
that SSPOS is a 5-bit field, with SSPOS bit 4
not-adjacent. This is for backwards compati-
bility in 16 bits/sample modes with TM-1000/
1100.
If DATAMODE=MSB first, transmission
starts with the MSB of the sample, i.e. bit
15 for 16 bits/sample modes or bit 31 for 32
bits/sample modes. SSPOS determines
the bit index (0..31) in the parallel input
word of the last transmitted data bit.
If DATAMODE=LSB first, SSPOS deter-
mines the bit index (0..31) in the parallel
word of the first transmitted data bit. Bits
SSPOS up to/including the MSB are trans-
mitted, i.e. up to bit 15 in 16 bits/sample
mode and bit 31 in 32 bits/sample mode.
See
Table 9-6
for more information.
CLOCK_EDGE 0
the parallel to serial converter samples
AO_WS on positive edges of AO_SCK
and outputs data on the negative edge
of AO_SCK (RESET default).
1
the parallel to serial converter samples
AO_WS on negative edges of AO_SCK
and outputs data on positive edges of
AO_SCK.
WS_PULSE
0
emit 50% AO_WS (RESET default).
1
emit single AO_SCK cycle AO_WS
NR_CHAN
00
Only AO_SD1 is active
01
AO_SD1 and 2 are active
10
AO_SD1, 2 and 3 are active
11
AO_SD1..SD4 are active
Each SD output either receives 1 or 2 chan-
nels depending on TRANS_MODE mono
resp. stereo. Non-active channels receive 0
value samples. In mono modes, each chan-
nel of a SD output receives identical left &
right samples. See also
Table 9-10
.
LEFTPOS(9)
RIGHTPOS(9)
DATAMODE
SSPOS
Table 9-6. Bits transmitted for each memory data
item S
operating mode
first
bit
last
bit
valid
SSPOS
values
16 bits/sample, MSB-first
16 bits/sample, LSB-first
32 bits/sample, MSB-first
32 bits/sample, LSB-first
S[15]
S[SSPOS] S[15]
S[31]
S[SSPOS] S[31]
S[SSPOS] 0..15
0..15
S[SSPOS] 0..31
0..31
Table 9-7. Minimum serial frame length in bits
operating mode
minimum serial frame length
16 bits/sample, mono
32 bits/sample, mono
16 bits/sample, stereo
32 bits/sample, stereo
13 bits
13 bits
13 bits
36 bits