At 04:19 PM 10/27/95 -0500, you wrote:
>> At 11:32 PM 10/26/95 -0500, you wrote:
>  [supercat]
>> >Is it possible, when using an external oscillator, to have the chip wake
>> >instantly from sleep mode (if the oscillator is running?)  Normally the
>> >16c5x and 16cxx have an oscillator startup timer except in the RC mode.
>> >Can the RC mode by made to accept an external oscillator signal (via some
>> >suitable resistor or capacitive coupling perhaps?)
>  [hobbes]
>> Here is the deal, as far as I can tell.  In RC mode you will always have a
>> 72ms power-up.  In all others you can have either '1024 osc cycles' or '72ms
>> + 1024 osc cycles'.  This is in all the 'xx data sheets, pg 16 of the '84
>> data sheet.
>>
>>            PWRTE=1      PWRTE=0
>> ---------------------------------------
>> xt,hs,lp | 72ms +     | 1024 tosc
>>          | 1024 tosc  |
>> ---------------------------------------
>> rc       | 72ms       |
>> ---------------------------------------
>
>Right, for powerup those timings apply.  For a reset from sleep, however,
>only the 1024tosc [if XT, HS, or LP] is applied [nothing at all if RC].  My
>question is whether it's possible to use the RC mode with an external osc-
>illator so as to dispense with the extra 1024tosc.
>
>
The answer is no with an external osc.  When programmed as an RC the PIC is
driving osc1.  On osc1 when the V gets to a certain level (say 4V) the pic
pulls it down.  When it pulls it to some low level (say 1V) it lets it go to
float back up, and so on.  On osc2 it is clocking out osc1/4.

Hope this helps..

Jim was here just a moment ago...