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PIC clock source.

I

ian field

Jan 1, 1970
0
Since the blank PIC doesn't know the type and configuration of its clock
until its programmed with that info, does that mean that a crystal or EXT CR
need not be present during programming?

TIA.
 
R

Richard Seriani

Jan 1, 1970
0
ian field said:
Since the blank PIC doesn't know the type and configuration of its clock
until its programmed with that info, does that mean that a crystal or EXT
CR
need not be present during programming?

TIA.

Ian,

If you are thinking about in-circuit serial programming, you may want to
read Olin Lathrop's article here:
http://www.embedinc.com/picprg/icsp.htm

Also, the Microchip In-Circuit Programming (ICSP) Guide is available from
the Microchip site.

If you are thinking about a stand-alone programmer, then the PIC wouldn't
have anything connected to it, anyway.

Richard
 
P

PhattyMo

Jan 1, 1970
0
ian said:
Since the blank PIC doesn't know the type and configuration of its clock
until its programmed with that info, does that mean that a crystal or EXT CR
need not be present during programming?

TIA.

No clock needed for programming,it seems to be clocked from the
programmer lines (data,clock,Vpp[+13V])
 
J

Jon Slaughter

Jan 1, 1970
0
ian field said:
Since the blank PIC doesn't know the type and configuration of its clock
until its programmed with that info, does that mean that a crystal or EXT
CR
need not be present during programming?

TIA.

The pics default to the internal oscillator. There are default configuration
bits.

For programming the clock is external an supplied by the PGCx line. The data
is clocked in so the internal oscillator is not used(well, except for some
internal stuff but not for sending commands and receiving data.
 
I

ian field

Jan 1, 1970
0
Jon Slaughter said:
The pics default to the internal oscillator. There are default
configuration bits.

For programming the clock is external an supplied by the PGCx line. The
data is clocked in so the internal oscillator is not used(well, except for
some internal stuff but not for sending commands and receiving data.

The task in hand is that I have tutorials from a number of different sources
and each author seems to have their own favourite clock frequency, for
example most of the assignments in the PIC in practice use 32.768kHz clock.

To make it easier to try assignments from different tutorials I've decided
to build a multi-frequency clock generator that can be connected to whatever
project board I happen to be using, instead of having to keep swapping
crystals and loading capacitors for the different clock frequencies.

If the clock isn't needed during programming then there's no need to make
provision to connect the clock module to any of the programming header
boards I build.
 
M

Marra

Jan 1, 1970
0
But the PIC defaults to a certain OSC type !
It doesnt just have none.
 
I

ian field

Jan 1, 1970
0
Marra said:
But the PIC defaults to a certain OSC type !
It doesnt just have none.

Of course not - one of the ICSP pins is a clock signal, I wanted to know if
that alone is sufficient during programming.
 
B

Ben Jackson

Jan 1, 1970
0
Since the blank PIC doesn't know the type and configuration of its clock
until its programmed with that info, does that mean that a crystal or EXT CR
need not be present during programming?

You mean like an AVR does? No. You can program it with no clock at all.
 

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