
Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 18: SPDIF Input
PNX15XX_SER_3
Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2006
18-5
The format in memory for both little and big-endian byte ordering is shown in
Figure 52.3.4
Bandwidth and Latency Requirements
Normally, the rate of transmission of frames corresponds exactly to the source
sampling frequency. The maximum latency requirement will be for 96 kHz streams
(i.e. frame rate = 96 kHz) with the SPDIF Input input set up for any of the 32-bit
capture modes:
(96K frames/sec) x (8bytes/ frame) = 0.768Mbytes/sec
The maximum latency allowed in order to sustain this transfer rate is (assuming data
transfers are 64 bytes each):
64 bytes/N sec= 0.768 Mbytes/sec
Solving for N and providing a relation,
(14)
For error-free operation during sustained DMA, there needs to be one 64 byte DMA
write transfer completed to memory every 83 usecs. This guarantees the latency
requirement for the worst case input sample rate. If the latency requirement is not
met, the hardware sets the HBE bit in the SPDI_STATUS register to logic ‘1’
indicating a bandwidth error. For this condition, one or more audio samples have
been lost and are not recoverable. The bus arbitration for the SPDIF Input input block
should be adjusted by the user to satisfy this latency requirement. Refer to section
Section 3.2 for details on SPDI_STATUS and other registers.
Figure 5:
Endian Mode Byte Address Memory Format
Little Endian
16-bit Stereo
etc.
msbyte
lsbyte
L: Left
R: Right
Note: n, n+1, n+2, n+3 refer
n
n+1
n+2
n+3
31
15
0
Big Endian
16-bit Stereo
etc.
31
15
0
or raw
32-bit Stereo
etc.
n+3
31
0
Little Endian
n
n+7
n+4
31
0
or raw
32-bit Stereo
etc.
31
0
Big Endian
31
0
to increasing byte addresses
within a naturally aligned 32-bit
memory address. (i.e. n = 0x0,
0x4, 0x8,0xC, etc.)
n
n+1
n+2
n+3
msbyte
lsbyte
msbyte
lsbyte
msbyte
lsbyte
msbyte
lsbyte
L
R
L
R
L
R
L
msbyte
lsbyte
msbyte lsbyte
msbyte
n+3
n
n+7
n+4
N
83.33uSec
≤