Can the mup21 take an external clock?

[e.matejowsky@xxxxxxxxxx (Eddie Matejowsky)]

>Figure on a refresh every 16 us.  That would be 64 KHz.  The refresh 
>instruction occurs only every 4 instructions, for a clock rate of
>256 KHz.  However, these refresh rates are enormously conservative.
>I would try 32 KHz as a conveniently available part.
>
I've just had a look in a "farnell" catalog for xtals, they've got .3072 meg
xtals for $20 AUS compared to $1.50 for a watch xtal. Does it really need to
be a xtal? Is there a way to use an rc or external clock? If you can then a
555 (and a
flipflop to square it up) would make a cheap refresh oscillator.
Eddie.M

Edward Matejowsky.
Queensland University of Technology
Centre for Eye Research
email E.MATEJOWSKY@QUT.EDU.AU
Wk +61 7 864 5731 Hm +65 7 2825382

There is nothing permanent except change.