
Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 17: SPDIF Output
PNX15XX_SER_3
Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2006
17-4
3.3 Data Formatting
3.3.1
IEC-60958 Serial Format
Figure 1 shows the serial format layout of an IEC-60958 block. A block starts with a
special “B” preamble, and consists of 192 frames. The sample rate of all embedded
audio data is equal to the frame rate. Each frame consists of 2 subframes. Subframe
1 always starts with an “M” preamble, except for subframe 1 in frame 0, which starts
with a “B”. Subframe 2 always starts with a “W” preamble.
When IEC-60958 data carries two-channel PCM data, one audio sample is
transmitted in each sub-frame, “l(fā)eft” in sub-frame 1 and “right” in sub-frame 2. Each
sample can be 16-24 bit, where the MSB is always aligned with bit slot 27 of the sub-
frame. In case of more than 20 bits per sample, the Aux eld is used for the 4 LSB
bits.
When IEC-60958 data carries non-PCM audio, such as 1 or more streams of
encoded AC-3 data and/or MPEG audio, each sub-frame carries 16 bits data. The
data of successive frames adds up to a payload data-stream which carries its own
burst-data.
This is described in the “Interface for non-PCM Encoded Audio Bitstreams Applying
IEC958.”
Philips Consumer Electronics, June 6 1997, IEC 100c/WG11 (preliminary
for IEC-61937).
Figure 1:
Serial Format of a IEC-60958 Block
channel 1
M
channel 2
W
channel 1
B
channel 2
W
channel 1
M
channel 2
W
Start of block (indicated by unique B pre-amble)
sub-frame 1
sub-frame 2
frame 0
frame 1
channel 1
M
frame 191
0
31
28
24
20
16
12
8
4
Sample data
L
S
B
M
S
B
B, W or M
pre-amble
Aux.
VU C P
Validity flag
User data
Channel status
Parity bit
sub-frame (2 channel PCM)
0
31
28
24
20
16
12
8
4
16 bits data
L
S
B
M
S
B
B, W or M
pre-amble
VU C P
Validity flag
User data
Channel status
Parity bit
sub-frame (non-PCM audio)
unused (0)