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

[richard]

use The DSM module with clock as carrier source and switich it on/off with the MDBIT bit in the MDCON register under control of a counter

[CuriousOne]

Yes, I need duty cycle of 50%, this is for HSS strobe application.

LATA makes no difference in speed, already tried.

can HPWM generate 4mhz signals? and counter, count them?

What is DSM module?

[HenrikOlsson]

Like I said, LATA has nothing to do with the speed but will help you from getting into another read-modify-write problem. Feel free to ignore....

DSM is digital signal modulator, a peripheral available on the 16F1829, see section 23 in the datasheet.

According to the manual the maximum frequency for HPWM is 32768Hz but that doesn't stop you from configuring the CCP module manually. At 32MHz it should be capable of generating 4MHz (but not 4mHz). Check out the Reference Clock Module as well, might be better than the CCP module as Richard suggests.

/Henrik.

[CuriousOne]

I had issue with read-modify-write on 628A. 1829 in same conditions works just fine.

[Art]

RWM again lol.

Some ideas...

Slower, but at least it’s 50% duty cycle

‘ Not RWM safe!

flipflop var bit

cycle:
flipflop = flipflop + 1
portb.0 = flipflop
goto cycle

can you afford to waste a whole port?

‘ Is RWM safe!

flipflop var byte
flipflop = %01010101

cycle:
portb = flipflop
@comf _flipflop
goto cycle

faster than what you posted above.
You need two consecutive nop instructions to balance the goto for %50 duty cycle in the loop you posted.

[CuriousOne]

Thanks, but how control amount of cycles?

[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