This is indeed the kind of info I am looking for.  Thanks!!

FWIW I am thinking that an alternative to using a PIC and an ISD chip
may be using a PIC and a 2nd PIC with extra memory.  The 2nd PIC
would be dedicated to making (8 bit mono) sound, getting samples out
of memory and sending PWM analog to a speaker and almost nothing else.

Every once in a while the main PIC would interrupt the sound PIC to
say "play sample number N now", and it would be OK if that stopped
sound playback.

So maybe this is an option.  If anyone sees a killing problem,
though, please let me know...I am still a beginner...

thanks, Philip

At 4:48 PM +1000 10/22/01, David Lions wrote:
>----- Original Message -----
>From: "Philip Galanter" <pg1@ACF2.NYU.EDU>
>To: <PICLIST@MITVMA.MIT.EDU>
>Sent: Monday, October 22, 2001 6:55 AM
>Subject: [EE]: I2C EEPROM - fastest, biggest, baddest is ???
>
>
>>  Hi all.  Another beginner question.  Still thinking about
>>  alternatives to the ISD analog sound chips.
>>
>>  Read about the I2C serial interface and am starting to understand it.
>>  But wondering if I2C EEPROM's are too small to use to store sampled
>>  sound.  Are these available in 1 MB or larger?  Vendors/part #'s?
>>  How many bytes per second can be read if the microcontroller is doing
>>  little else?
>>
>>  thanks!  Philip
>>
>>  --
>>  http://www.piclist.com hint: The PICList is archived three different
>>  ways.  See http://www.piclist.com/#archives for details.
>>
>>
>
>The company I used to work for made telephony cards that had voice recording
>and playback features.  We used CODEC chips to compress and de-compress the
>voice, and then stored it on SPI FLASH chips.
>
>You specifically requested I2C and EEPROM.  Our chips were SPI and FLASH.
>The part number was Atmel AT45D041.  The SPI does a 10MHz clock rate max.
>The AT45D041 is a ~4megabit part.  The flash pages are slightly bigger than
>256bytes.
>
>We chose them because at the time (bout 2 years ago) they were cheapest per
>unit storage.  They were AUD$7, which is about USD$3.5 now.  Atmel didn't
>have a fab so they were hard to get, but with the economic downturn supply
>should be easy now.
>
>As for speed, I vaguely remember calculating something like 50kbyte/s write
>speed.  The big bottleneck is your processor.  We used a Motorola 68??? (i
>forget which, it had built in ISDN interfaces).  The problem is that you
>have to *POLL* the SPI interface of the processor (no interrupt,
>inefficient).  Plus, it's buffer is only 1 byte, so the overhead of
>reading/writing streams is very large.  You will have the exact same problem
>with the PIC.  No matter how fast the FLASH chip is, SPI interfaces in PIC's
>and CPU's are designed for reading real-time-clocks, not streaming lots of
>data.
>
>If you are only doing one channel of sound, and not much else in the mean
>time, you will be ok.  Unfortunately for us it wasn't ok and the company is
>now broke after lots of mistakes like this.
>
>But anyway, look at Atmels serial dataflash.  They are basically the
>cheapest.
>
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