Simple asm delay ?

[ultiblade]

Hi All !

I'm kinda stuck @ the moment. I have a 12F683 and i need to do a variable delay ranging from 1us to 1000us.

The problem is that at 8Mhz the pauseus can't go as low as 12us.

Does anybody have a asm routine or macro that can be used here ?

Something like :

Macro delay(time in us)
if time = 1 then
nop
nop
if time = 2 then
nop
nop
nop
nop
if time = 3 then

etc, etc ...

Thanks !

[mikendee]

I think that you could use something like.

Delay Var Word ' Pause in us
Counter Var Word

FOR Counter = 1 to Delay
@nop
@nop
NEXT Counter

It's untested so I'm guessing it should work but I don't know how long the LOOP will add to the pause.

Regards, Mike

[Jerson]

Assuming a 8MHz clock, some ASM macros

delay1us macro
    goto $+1      ;  2 cycle delay
                endm

delay2us macro
    delay1us
    delay1us
               endm

delay4us macro
    delay2us
    delay2us
               endm

delay8us macro
    delay4us
    delay4us
               endm

Now, you may want to get something like 5 us. For that you can
@ delay4us
@ delay1us
in your code

Hope this is helpful to you.

[ultiblade]

Wow, Thanks.

I'm gonna try this. Tried the for..next just yet but it won't go below 5us delay.

Jerson, i think this would do the trick, but i need to figure out how to let the software 'choose' the right delay .. I need to be able to feed the number of uS to delay to the asm macro.

Something like ...

ASM
Delay1us  macro time
for x = 0 to time
    goto $+1
next
ENDASM

[Acetronics2]

Hi,

The 683 has a TMR1 and also a CCP module ...

just use one of them for variable delays !!!

see asm examples in the relevant Datasheet chapter ...

may be 1 and 2 microseconds will need a "special treatment" ...

Alain

[ultiblade]

You are so right !

The thing is however, i have tmr1 setup as a counter and i use its overflow to sync the whole program on 100hz.

I have three different led's that are driven by fet's. Each led has it's own channel and due to the design of the driver, at a given moment only 1 led me be high.

To be able to shift the colors around, i turn on a certain channel for a certain ammount of time.

RED con %001
GRN con %010
BLU con %100 

loop60
    if ledred = 0 then goto noRED
    GPIO = red
    pauseus ledred
noRED:
    if ledgrn = 0 then goto noGRN
    GPIO = grn
    pauseus ledgrn
noGRN:
    if ledblu = 0 then goto noBLU  
    GPIO = blu
    pauseus ledblu  
noBLU:
goto loop60

Once interrupted the ledred / ledgrn / ledblu values are altered, but always in a way that ledred+ ledgrn + ledblu = 1000, the timer get's a reset and it then jumps back into the loop.

The example above works but pauseus can't delay faster then 12us ...