--- In anand bhavnani <> wrote:
>
> As u have mentioned the processor handles flash through the cpld and
additionally cpld perfoms several other functions.
>
> so can i assume that the cpld is on the board primarily because the
processor in itself is not having a controller (like uart
controller,VEC. INT. ,...etc) that could have effectively interfaced
with the flash and hence the need for cpld arose.
no. IMHO, having dedicated "NAND flash controller" pins implemented
on a CPU would only serve to waste pin real-estate on the CPU package.
Interfacing NAND flash chips isn't rocket science (Its implemented in
just a 72-macrocell CPLD after-all) The CPLD already is needed and
cost-justified for other duties it has on the board, so we really got
NAND support for "free". If it were on the Cirrus CPU, we'd be paying
Cirrus for that (imaginary) NAND interface on every TS-7xxx board
whether or not we actually even had a NAND chip in the design. When
it comes down to it, the SMC bus is perfectly fine for NAND flash chips.
Almost all of the boards we design have a CPLD (or an FPGA such as the
TS-7260 or TS-7300) on them and only the TS-7250 and 7260 have NAND
flash chips. It gives much design flexibility and helps to keep the
number of discrete chips low. We also can custom program the CPLD for
customers with special needs without having to do a (more expensive)
board redesign. (e.g. DIO pins that do quadrature or PWM instead of
just regular in/out)
Also, there is subtle "secret sauce" in the CPLD code that deters a
casual Joe Engineer from using the published schematics to
remanufacture or create new CPLD code for themselves. Or at least one
that will work reliably. Likely, a wrong CPLD load would even cause
boards to self-destruct in very unique ways. TS reserves this CPLD
code, the PCB gerbers, and full schematic details for customers who
license the design while releasing most of the rest to the public domain.
Usually, getting sound is best approached with a $10 USB sound dongle.
Using the CPU to simultaneously sample the ADC at 10-40 KHz, feed a
raw DAC chip and run Linux or any other type of processing is just
asking for trouble. Such a job is cake for a DSP, but a general
purpose CPU running an operating system really likes more hardware
help than the typical raw ADC/DAC provides. (for instance, FIFO's and
a sampling clock generator)
//Jesse Off
>
> also please suggest a DAC that i may use to provide the sound
support to the board considering the fact that i am using MAX197 12
bit ADC.
>
> thanks,
> //anand.
>
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