
Functional Overview
1-5
The MPEG and Dolby Digital audio formatters reformat encoded
Musicam and Dolby Digital streams, respectively, into S/P DIF bursts.
This process preserves the Musicam multichannel extensions (no
downmixing), as well as the multichannel Dolby Digital format, for
S/P DIF output of true surround sound. Version L64021D adds a DTS
audio formatter to the MPEG and Dolby Digital formatters.
1.2.3 Host Interface
The Host Interface includes 512 8-bit registers (some not used), read
and write FIFOs, and byte enable logic. The host and L64021
communicate exclusively through the registers. An external interrupt
signal from the L64021 alerts the host when register contents are
changed. Separate I/O signals are used for handshaking. The L64021
supports either an Intel or Motorola type processor by tying an external
pin high or low.
The read and write FIFOs are used to give the host access to the
external SDRAM. The read/write paths are still through registers. The
interface supports direct read/write, DMA transfers using an external
DMA controller, and block moves within SDRAM. The byte enable logic
converts host byte writes to 8-byte words for the write FIFO and 64-bit
internal bus and vice versa. The byte enable logic also switches byte
order for little endian hosts.
1.2.4 Channel Interface
The L64021 includes an independent parallel interface for direct
connection to DVD drives. The interface uses a simple handshaking
signal for bitstream transfers to memory.
The L64021’s channel interface handles the incoming data, which is
assumed to be an MPEG-2 compliant bitstream, and provides error
detection, reporting, CSS descrambling, and disc/title key authentication.
The channel interface detects data in the bitstream that does not meet
MPEG-2 or Dolby Digital syntax and can ag the data for exception
processing.