Crystal DSP Board Operation and Debug
" SPMUXCTL0-2 -- The three SPDIF MUX address control bits. These
bits select which of 6 SPDIF inputs are routed to the CODEC.
" \DSPMUXSEL -- This bit selects which DSP I2S outputs are routed to
the CODEC. This is necessary to accommodate support of an
expansion DSP for something like THX post processing.
" \DSPMUXSEL = 0 selects the MAIN DSP outputs to the CODEC. This
configuration is used for all applications except those which
require post-processing, like THX.
" \DSPMUXSEL = 1 selects the EXPANSION DSP outputs to the CODEC.
" For THX, the MAIN DSP will complete most signal processing,
pass the processed signal on (via its? I2S output) to the
Expansion DSP, which will do the THX post processing and
then the Expansion DSP outputs will be sent to the CODEC.
" \uC15-18 -- These four bits select the DSP PROM Page address to
point to one of sixteen 32KB pages for different DSP code
algorithms (or DSP tables like DTS tables). Each DSP code
algorithm set consists of a maximum of 32KB of code.
" The exception to this is that DTS tables require 64KB. How
this is handled is described in the section on the DSP ?EPROM?
function.
" EXP_PIOA_SERDATOUT -- This signal is used currently only for the
Festival 100 product.
" It allows the DSP board CPU to control another parallel I/O
port on one of the Festival boards for digital tone control.
" NOTE that the 6-pin JP4 connector is used exclusively for this
interface on Festival. There is no other use for JP4.
2.5 DSP/CODEC
This function consists of the DSP and CODEC chips and some 5V to 3V
buffers for interfacing the 3.3V DSP chip to the +5V CPU chip.
2.5.1 DSP Chip
The Crystal DSP chip is the heart of the DSP board digital decoder
function. The DSP chip supports the following functions:
" Auto boot -- the DSP chip executes its? microcode from an internal
32KB RAM. This RAM is downloaded from an external EPROM. The DSP
chip will automatically read in the currently selected 32KB page of
external memory when the CPU initiates the DSP auto boot sequence.
This auto boot of code takes about 80 msec, plus some other setup
delays. So, it takes about 100-200 msec to auto boot or switch
modes. The user sees this minor delay when switching from one mode
type to another via the User Interface (remote control of On Screen
Menu).
" \EXTMEM - External memory access enable
" \EMOE - External memory data output enable
" D0-D7 - Multiplexed external memory address / data bus.
" Sharing Auto Boot EPROM -- two DSPs (MAIN and EXPANSION) share the
same boot PROM when both are present. This keeps the expansion
DSP board very simple and inexpensive.
" SPI bus communication interface -- the DSP communicates with the CPU
via a SPI protocol. This simple serial interface requires only a
02/23/05 8 |
ACEC
HARMAN KARDON
