16F887 20Mhz External Clock Problems

[skimask]

Echo'ing Joe's reply...
Slower resonators (i.e. <8Mhz)...no problems on the messy/quicky boards...
Faster resonators (i.e. above 10Mhz or so)... Gotta be a clean set up, good solder joints, short runs, clean power, and so on...

[BrianT]

I almost always prototype my designs piece by piece on solderless breadboards. That is probably why I am getting dodgy results with fast resonators.

If the solderless version does not work I am most reluctant to build a pcb on the wish that it might with a better layout. I also use a couple of general purpose boards like those from OLIMEX and my own designs but these all have crystals.

thanks
BrianT

[Acetronics2]

Hi,

Some idea here ???

4.6 Clock Switching
The system clock source can be switched between
external and internal clock sources via software using
the System Clock Select (SCS) bit of the OSCCON
register.
4.6.1 SYSTEM CLOCK SELECT (SCS) BIT
The System Clock Select (SCS) bit of the OSCCON
register selects the system clock source that is used for
the CPU and peripherals.
• When the SCS bit of the OSCCON register = 0,
the system clock source is determined by
configuration of the FOSC<2:0> bits in the
Configuration Word Register 1 (CONFIG1).
• When the SCS bit of the OSCCON register = 1,
the system clock source is chosen by the internal
oscillator frequency selected by the IRCF<2:0>
bits of the OSCCON register. After a Reset, the
SCS bit of the OSCCON register is always
cleared

Alain