Generating a series of high frequency pulses with pre-defined length.

[richard]

‘ Is RWM safe!

flipflop var byte
flipflop = %01010101

cycle:
portb = flipflop
@comf _flipflop
goto cycle

doing it that way won't get past a few hundred kilohertz






its easy with the dsp module ,but the last pulse is difficult to control
if being 1 pulsE short sometimes this works great for a 4MHz output stream

'****************************************************************
'*  Name    : MODULATOR.BAS                                     *
'*  Author  : richard                    *
'*  Notice  : Copyright (c) 2016 [select VIEW...EDITOR OPTIONS] *
'*          : All Rights Reserved                               *
'*  Date    : 5/29/2016                                         *
'*  Version : 1.0                                               *
'*  Notes   :  4MHZ CARRIER FOR X PULSES   x=10 to 65535        *
'*          : 16F1825                                           *
'****************************************************************
  #CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF            
#ENDCONFIG
 
OSCCON=$70 
DEFINE OSC 32
@TIMER1=TMR1L
'                       PIC 16F1825
 
TRISA     = %111111    ' Make all pins Input 
trisc     = %101111  ;Make all pins Input   
ANSELA=0     
ANSELC=0

CLKRCON=  %11110011
MDCON=    %11000000
MDSRC=    %00000000
MDCARH   =%00100011
MDCARL   =%00000000
X VAR WORD    
TIMER1     VAR WORD EXT
'  ;debug   --------------------------
' TRISA.0     = 0
' lata.0=1
' pause 2000     ;debug
' serout2 PORTa.0,84, ["ready v3",13,10 ]    ;debug
'  ;debug ------------------------------------
; moddout is portc.4
X=40

Main_Loop:     
TIMER1=~(X-6)
ASM 
    BCF  PIR1,0
    MOVE?CT 1,MDCON,0
    MOVE?CB 0X71,T1CON
COFF    
    BTFSS PIR1,0 ;    
    BRA COFF
    
    MOVE?CT 0,MDCON,0
    MOVE?CT 0,T1CON,0
ENDASM
PAUSE 200 
goto Main_Loop
end

[Art]

Yes of course hardware will be faster, but neither are the original examples.
I’m not saying it’s possible to get a 4MHz signal that way in software, just faster than what was posted.