Oscillator question and measurement

**Acetronics2** · - 24th February 2013, 23:03

a little MPSIM ( MPLAB ) simulation - supposed to be relatively true - gives à 3.2µs half -cycle to your test ... around 160 khz output frequency !
BTW ... I'm not sure the DEFINE OSC 48 and a 20 Mhz Xtal to be a good combination ...

best result @ 1.8µs half cycle given by

Code:

Portb.1 = ! Portb.1

instead of TOGGLE + PAUSEUS1

**Christopher4187** · - 25th February 2013, 03:11

Here are the results. Are these typical?

Code:

start:
pauseus 1
toggle portd.1
goto start

375 KHz

Code:

start:
toggle portd.1
goto start

1 MHz

Code:

start:
Portb.1 = ! Portb.1
goto start

This does nothing

Code:

start:
portd.1=1
portd.1=0
goto start

3 MHz

**Acetronics2** · - 25th February 2013, 20:47

Originally Posted by Christopher4187

Code:

start:
Portb.1 = ! Portb.1
goto start

This does nothing

Sure it does not show anything on portD1 ...

Alain

**Christopher4187** · - 25th February 2013, 20:53

I know. I was too lazy to edit it yesterday. My original comment still stands.

**Acetronics2** · - 25th February 2013, 21:59

ohhh ... may be the RMW issue ...

due to a 18F chip ... I should have written:

Code:

start:
latb.1 = ! latb.1
goto start

on test with the EP5 tomorrow morning ...

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