Eratic Behavior while using CTR

DDS

Help Please.

I have spent hours trying to track down the problem here.
Looking at the attached .spin file, when it runs, often within the first 20-30· cycles, it jumps ahead by thousands.
I can't use the waitcnt in this application. (I have stripped out all of the unnecessary code)

If I had to guess, I would say that the problem is timing as the cog cycles in/out of the hub.
If I get rid of the wrlong statement, it seems to work fine.
Any help would really be appreciated, I am just starting out.

Thanks,

Don

(snippet below, full spin file attached)
············· org
asm_entry
············· mov······ dira,ledport
············· mov······ seconds,#0
············· jmp······ #:LoopInit·············
:loop········
············· cmp······ hs,cnt wc······················ ' Set C=1 if cnt>hs····
······· if_nc jmp······ #:loop························· ' not done with time
:LoopInit
············· mov······ hs,cnt························· ' load 1-Second timer
············· add······ hs,CPS
············· add······ seconds,#1····················· ' Increment seconds
············· mov······ st, seconds····················
············· shl······ st, #16
············· mov······ outa,st
············· wrlong··· seconds, trigaddr·············· ' Write Value to pass-through·············
············· jmp······ #:loop

Mike Green

Your problem is the comparison between hs and cnt when they have opposite signs. It's better to save the starting time of the interval and subtract that from the current time. When the result is greater than one second (CLKFREQ, not CLKFREQ/2), another second has gone by:

asm_entry  mov  dira,ledport
                  mov  seconds,#0
new_time   mov  hs,cnt
loop            mov  temp,cnt
                  sub   temp,hs
                  cmp  temp,CPS  wc
     if_c        jmp  #loop
                  add   seconds,#1
                  mov  st,seconds
                  shl    st,#16
                  mov  outa,st
                  wrlong  seconds,trigaddr
                  jmp  #new_time

DDS

Mike,

Thanks for the solution!

Don