L64005 MPEG-2 Audio/Video Decoder Technical Manual
3-11
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
are two basic modes of operation: master mode and slave mode,
selected by clearing or setting EXCLK (Group 6 Register 48 bit 0)
respectivley. In master mode, the L64005 generates BCLK and LRCLK
from the SYSCLK clock reference using an internal divider. Jittering the
BCLK and LRCLK signals yields, on average, an accurate audio sample
rate. In slave mode, the L64005 takes the oversampling clock reference
provided on the ACLK pin as an accurate external DAC clock reference.
Typically, this clock is either 256 or 384 times the sampling frequency.
The L64005 downsamples this reference clock to produce jitter-free
BCLK and LRCLK signals.
BCLK
Serial DAC Bit Clock
Output
BCLK is an output clock with programmable frequency.
Clocks the ASDATA bit into the DAC on its rising edge.
BCLK can be set under program control. See
Chapter 7,LRCLK
Serial DAC Left/Right Clock
Output
LRCLK is an output clock with programmable frequency.
LRCLK indicates which samples belong to the left and
right stereo channels. This signal can be programmed to
be active HIGH or active LOW. Set the LRP bit in Group
6, Register 48 to reverse the polarity of LRCLK.
ASDATA
Audio Serial Data Line
Output
ASDATA carries serial audio data. The format is program-
ACLK
External Audio Clock
Input
When in slave mode, this clock is used as a reference for
the audio output stage. It is typically either 256 or 384
times the audio sampling frequency, as determined by
the programmable NCO. Refer to the subsection entitled
3.6
PLL Interface
The PLL interface supports L64005’s on-chip PLL module.
AGND
PLL Analog Ground
Input
AGND connects to a ground plane that isolates AGND
from the digital plane of the L64005 chip. This isolated
connection helps avoid noise that could propagate from