PNX1502E Datasheet, PDF (506/819 Pages) NXP Semiconductors – Connected Media Processor

Philips Semiconductors
Volume 1 of 1
PNX15xx Series
Chapter 15: Audio Output
2.4 Interrupts
Audio Out has a level triggered interrupt request signal. An interrupt is asserted as
long as any of the UNDERRUN, HBE, BUF1_EMPTY or BUF2_EMPTY condition
flags are asserted. and the corresponding INTEN bit is enabled. Interrupts are sticky
(i.e., an interrupt remains asserted until the software explicitly clears the condition
flag by an ACK action).
Remark: For legacy reasons, the MMIO interrupt mechanism for Audio Out has not
been changed.
2.4.1 Interrupt Latency
During normal error free transmission, the source of an Audio Out interrupt will be
from BUF1_EMPTY and BUF2_EMPTY. The DMA buffer size configured in the
AO_SIZE register will directly affect the frequency of these ‘empty’ interrupts.
Software should set up the AO_SIZE register with a large enough value so that
interrupts occur no more frequently than 1 ms in order to meet system interrupt
latency requirements.
2.5 Timestamp Events
Audio Out exports event signals associated with audio transmission to the central
timestamp/timer function in the system. The central timestamp/timer function can be
used to count the number of occurrences of each event or timestamp, the occurrence
of the event, or both. The event will be a positive edge pulse with the duration of the
event to be greater than or equal to 200 nS. The specific event exported is:
• BUF_DONE — The occurrence of this TSTAMP event indicates that the last word
of the current DMA memory buffer has started to be sent out on the serial data
port.
This event represents a precise, periodic time interval which can be used by system
software for audio/video synchronization.
2.6 Serial Data Framing
The Audio Out unit can generate data in a wide variety of serial data framing
conventions. Figure 3 illustrates the notion of a serial frame. If POLARITY = 1, a
frame starts with a positive edge of the WS signal. If POLARITY = 0, a serial frame
starts with a negative edge on WS. (See Section 4. on page 15-15.) If
12NC 9397 750 14321
Product data sheet
Rev. 2 — 1 December 2004
© Koninklijke Philips Electronics N.V. 2002-2003-2004. All rights reserved.
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