Chris Eddy <PICLIST@MITVMA.MIT.EDU> wrote:

> The first lesson relates to the 93LC46 SPI bus EEPROM.  ....  I
> found that at a clock rate of 200Hz, the chip fails to function.
> If you peruse the databook, it indicates only a max limit at 2MHz.
> It says nothing about a minimum.  Sure enough, my other two
> projects were running faster, and an interrupt routine shuffle on
> the third project solved the problem.  The moral of the story is do
> not run EEPROMS too slow.

    Chris:

    The problem with running certain Microchip SPI EEPROMs too slowly
    is that the "Write Complete" signal goes away shortly after the
    EEPROM asserts it.  All other functions work fine no matter how
    slowly you clock the chip... You just have to check the "Write
    Complete" signal pretty often after sending a "write"
    instruction.

> The second lesson relates to the analog input on the '73. .... [I]
> found that the second piece of code, upon entering, disables
> interrupts briefly.  This disable occured in the timeline precisely
> where the interrupt for the analog result would arrive. The chip
> would presumably just hold the value and interrupt when GIE is set
> again, but I observed that it corrupted the analog input value.

    I've never seen this behavior... I suspect that the problem
    was caused by your software.

    -Andy

=== Andrew Warren - fastfwd@ix.netcom.com                 ===
=== Fast Forward Engineering - Vista, California          ===
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