> Using a basic compiled program using a for-next loop,  a flash PICchip.
> can I expect toget a pulse every 55 ms. or about 18pulses per second?
>
> I know a lot of it will depend on what speed I am running the chip at.

Yes, and on the BASIC compiler.

Let me see, hypothetically (non working code, just counting a bit):

FOR A = 0 TO 255
PORTC = PORTC & 254
PORTC = PORTC | 1
NEXT A

; FOR A = 0 TO 255
  movlw 0
  movwf A
  goto NEXT1002
NEXT1001
  movlw 255
  xorwf A,w
  btfsc STATUS,Z
  goto NEXT1003
  incf A,f
NEXT1002
; PORTC = PORTC & 254
  movlw 254
  andwf PORTC,f
; PORTC = PORTC | 1
  movlw 1
  iorwf PORTC,f
; NEXT A
  goto NEXT1001
NEXT1003

Which indicates there are 4 cycles of setup and 11 cycles per loop.
Given a not unreasonable clock frequency of 4 MHz, that means you get
a pulse every 11us, so about 90909 pulses per second.

As said, this highly depends on the clock frequency, but also on the
BASIC compiler (the code could be further optimized using
incfsz/decfsz, which would make it faster. Or the BASIC compiler
outputs more generic code, allowing values greater than 255, which
would make things slower... Also if it would allow full expressions in
the FOR loop this might add superfluous dummy variables, slowing
things down).

But 90909 pulses per second seems a lot closer to reality than 18. If
you DO want 18 pulses per second, you might need to add a suitable
PAUSE command, of known duration.

Greetings,
Maarten Hofman.

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