Path: utzoo!attcan!uunet!ginger.acc.com!ivucsb!todd
From: todd@ivucsb.sba.ca.us (Todd Day)
Newsgroups: comp.dsp
Subject: Re: More digital mixer stuff
Message-ID: <1989Sep30.122344.12326@ivucsb.sba.ca.us>
Date: 30 Sep 89 12:23:44 GMT
References: <9238@pyr.gatech.EDU> <7905@microsoft.UUCP>
Organization: Disillusioned Graduate Hackers, Santa Barbara, CA
Lines: 28

brianw@microsoft.UUCP (Brian Willoughby) writes:

~Sure, why overwork the DSP?  Question: how would you know which 16 bits
~make up a sample word?  I.e. are there some kind of start bits which
~could be used to signal an interrupt.  A good setup would involve
~clearing all the shift register bits to one state, and then shifting in
~until the start bit appears in the MSBit.  Whatever polarity the start
~bit is, just clear the shift register to the opposite value and interrupt
~the DSP when a full word is ready.

The serial port on the 56000 is completely independent of the ALU, etc
(i.e., it is like an on board peripheral).  I was talking about using
the synchronous serial input.  You supply it with a bit clock and a
word clock and it automatically does the serial to parallel conversion
*and* generates an interrupt when it's ready.  Usually, my programs for
my board consist of a main loop that does absolutely nothing and an
interrupt service routine.  The (nano)second I get a sample, the interrupt
routine starts executing.  My service routine loads the parallel data,
operates on it, and then stores it to the serial output buffer.  The
serial section of the chip then outputs the data when the next word
clock comes around, all independent of the *real* DSP hardware on the
chip.

-- 

Todd Day  |  todd@ivucsb.sba.ca.us  |  ivucsb!todd@anise.acc.com
"Ya know, some day these scientists are going to invent something
	that can outsmart a rabbit" -- Bugs Bunny