TM1100 Preliminary Data Book
Philips Semiconductors
9-8
PRELIMINARY INFORMATION
File: aout.fm5, modified 7/24/99
antee, the situation can arise that the 64 byte buffer is not
refilled and the holding register is exhausted by the time
a new output sample is due. In that case the HBE error
is raised. The last sample (or sample pair) will be repeat-
ed until the buffer is refreshed. The HBE condition is
sticky, and can only be cleared by an explicit ACK_HBE.
Given a sample rate
fs, and an associated sample inter-
val T (in nSec), the arbiter should be set to have a latency
of at most T-20 nSec for stereo 16-bit mode, 2T-20 nSec
for mono 16-bit and stereo 8-bit modes and 4T-20 nSec
information on arbiter programming.
The latency for 4,6 and 8 channel modes can be comput-
ed as if the system is operating in stereo mode with a 2x,
3x respectively 4x sample rate.
Table 9-10 shows the required arbiter latency settings for
a number of common operating modes. The rightmost
column in the table illustrates the nature of the resulting
64 byte highway requests. Is not required to compute ar-
biter settings, but may be used to compute bus availabil-
ity in a given interval.
9.11
ERROR BEHAVIOR
In normal operation, the DSPCPU and Audio Out hard-
ware continuously exchange buffers without ever failing
to transmit a sample. If the DSPCPU fails to provide a
new buffer in time, the UNDERRUN error flag is raised,
and the last valid sample or sample pair is repeated until
a new buffer of data is assigned by an ACK1 or ACK2.
The UNDERRUN flag is
not affected by ACK1 or ACK2;
it can only be cleared by an explicit ACK_UDR.
If an HBE error occurs, the last valid sample or sample
pair is repeated until the Audio Out hardware retrieves a
new sample buffer across the highway.
9.12
4, 6 AND 8 CHANNEL AUDIO
The TM1100 Audio Out unit is capable of generating a
bitstream with 4,6 or 8 channels of audio. This is only
supported if Audio Out is operating as serial master
(SER_MASTER=1). More than two channels of audio
Table 9-9. Audio Out MMIO Control Fields
Field Name
Description
RESET
Resets the audio-out logic. See
Sectiontion of the recommended procedure.
TRANS_ENABLE
Transmission Enable ag.
0
(RESET default) Audio Out inactive.
1
Audio Out transmits samples and
acts as DMA master to read samples
from local SDRAM.
Do NOT change the SER_MASTER and
POLARITY bits while transmission is
enabled.
SLEEPLESS
0
(power up default) Audio Out goes
into power down mode if TM1100
goes to power down mode.
1
Audio out continues operation when
TM1100 goes to power down mode.
Samples are read from memory as
needed, and Audio Out interrupts,
when enabled, will wake up the
DSPCPU.
BUF1_INTEN
Buffer 1 Empty Interrupt Enable.
0
(default) no interrupt
1
interrupt (SOURCE 12) if buffer 1
empty
BUF2_INTEN
Buffer 2 Empty Interrupt Enable.
0
(default) no interrupt
1
interrupt (SOURCE 12) if buffer 2
empty
HBE_INTEN
HBE Interrupt Enable.
0
(default) no interrupt
1
interrupt (SOURCE 12) if a highway
bandwidth error occurs.
UDR_INTEN
UNDERRUN Interrupt Enable.
0
(default) no interrupt
1
interrupt (SOURCE 12) if an
UNDERRUN error occurs
ACK1
Write a 1 to clear the BUF1_EMPTY ag
and remove any pending BUF1_EMPTY
interrupt request.
ACK1 always reads 0.
ACK2
Write a 1 to clear the BUF2_EMPTYag
and remove any pending BUF2_EMPTY
interrupt request.
ACK2 always reads 0.
ACK_HBE
Write a 1 to clear the HBE ag and
remove any pending HBE interrupt
request.
ACK_HBE always reads as 0.
ACK_UDR
Write a 1 to clear the UNDERRUN ag
and remove any pending UNDERRUN
interrupt request.
ACK_UDR always reads 0.
Table 9-10. Audio Out Highway Arbiter latency
requirement examples
TransMode
fs
(kHz)
T
(nSec)
max.
arbiter
latency
(nSec)
access
pattern
mono
8 bit/sample
8.0
125000
499,980
1 request
every
8,000,000 nS
stereo
16 bit/sample
44.1
22676
22,656
1 request
every
362,812 nS
stereo
16 bit/sample
48.0
20833
20,813
1 request
every
333,333 nS
stereo
16 bit/sample
96.0
10417
10,397
1 request
every
166,667 nS
6 channel
16 bit/sample
44.1
22676
7,539
1 request
every
120,937 nS
8 channel
16 bit/sample
44.1
22767
5,649
1 request
every
90,702 nS