Philips Semiconductors
PNX15xx Series
Chapter 16: Audio Input
Volume 1 of 1
12NC 9397 750 14321
Koninklijke Philips Electronics N.V. 2002-2003-2004. All rights reserved.
Product data sheet
Rev. 2 — 1 December 2004
16-3
2.1 Chip Level External Interface
The Audio In chip level I2S related external interface has seven pins AI_OSCLK,
AI_SCK, AI_WS and AI_SD[3:0]. These pins may be also referenced as OSCLK,
SCK, WS and SD[3:0].
The AI_OSCLK is a precise, programmable clock output intended to serve as the
master system clock for the external A/D subsystem. The AI_OSCLK is generated
from the Clock module which is outside the Audio In block. Although conceptually the
oversampling clock is an output at the chip level, at the Audio In block level, this is an
input. Six other pins constitute a flexible serial input interface IP.
AI_SCK = Audio In Serial Clock
AI_WS = Audio In Word Select
0 = Left Channel
1 = Right Channel
AI_SD[3:0] = Audio In Serial Data
Using the Audio In MMIO registers, these pins can be configured to operate in a
variety of serial interface framing modes, including but not limited to the following:
Standard stereo I
2
S (MSB first, 1-bit delay from WS, left and right data in a
frame). (For further details on I
2
S, refer to the “I
2
S Bus Specification” dated June
5 1996, in the
Multimedia ICs Data Handbook IC22
by Philips Semiconductors,
1998.)
LSB first with 1- to 32-bit data per channel
Complex serial frames of up to 512 bits/frame with “valid sample” qualifier bit
Table 1: Audio-In I2S Related Ports
Signal
Type
Description
AI_OSCLK
Input
Oversampling Clock. This can be programmed to emit any frequency up to 40 MHz with a
resolution of better than 0.3 Hz. It is intended for use as the 256 f
s
or 384 f
s
oversampling
clock by external A/D subsystem.It is also used by the Audio in block to generate AI_SCK
when it is in master mode. This is generated from the clock block, outside the Audio In
module. It is an output from the chip, but also an input to the Audio Input block.
AI_SCK
In/out
When Audio In is programmed as the serial-interface timing slave (power-up default), SCK is
an input. SCK receives the serial bit clock from the external A/D subsystem. This clock is
treated as fully asynchronous to the main chip level clock. When Audio In is programmed as
the serial-interface timing master, SCK is an output. SCK drives the serial clock for the
external A/D subsystem. The frequency is a programmable integral divide of the OSCLK
frequency.
SCK is limited to 30 MHz. The sample rate of valid samples embedded within the serial
stream is limited to 100 kHz.
AI_SD[3:0]
Input
Serial Data from external A/D subsystem. Data on these pins are sampled on positive or
negative edges of SCK as determined by the CLOCK_EDGE bit in the AI_SERIAL register.
AI_WS
In/out
When Audio In is programmed as the serial-interface timing slave (power-up default), WS
acts as an input. WS is sampled on the same edge as selected for SD. When Audio In is
programmed as the serial-interface timing master, WS acts as an output. It is asserted on
the
opposite edge of the SD sampling edge.
WS is the word-select or frame-synchronization signal from/to the external A/D subsystem.