help with pasm subroutines

Comments

• Ariba Posts: 2,693

  2018-12-16 06:01

  You still don't stop the cog at the end of the code. And you call the writer-subroutine at a point that never shoud be reached (between the subroutines).
  
  Also the unnecessary "mov x_var, temp_var" lines are still there. This will confuse a reader of your tutorial.
  
  Here is your 2 subroutine code with better indentions and the above issues corrected. I also renamed the temp_var to varptr, because that describes it better.
  

  {{Multiplication based on the propeller manual page 380}}
  
  CON
     _clkmode = xtal1 + pll16x
     '_xinfreq = 6_250_000   'MY BOARD AT 1OOMHZ  DIFFERENT CRYSTAL
     _xinfreq = 5_000_000  'QUICKSTART 80 MHZ  NORMAL CRYSTAL
  
  var
     'Spin variables
     long x             'we pass this address in par at cognew
     long y
     long product
     
  obj
     pst : "parallax serial terminal"
  
  
  pub main
     x := 3
     y := 9
     pst.start(115000)
     waitcnt(clkfreq*5 +cnt)      'hold five sec to open the
     'serial terminal and enable it
     cognew(@asm,@x)              'start cog at the first variable address
     waitcnt(clkfreq*2 +cnt)      'give pasm time to do the work
     
     pst.str(string("product:"))  'show a string on terminal
     pst.dec(product~)            'show decimal value of product on terminal
     pst.newline
       
  
  dat
  '
  asm                  org
  
                       mov varptr, par            'move par to the local varptr (points to x-var)
                       rdlong x_var, varptr       'read in the x value from Spin vars
                       add varptr, #4             'incr varptr to next long which is the y-var address
                       rdlong y_var, varptr       'read in the y value
                       add varptr, #4             'inc varptr to the product variable address
  
                       call #multiply             'multiply x with y
                       call #writer               'and write result to product var
  
                       cogid   t                  'stop the cog
                       cogstop t
  
  ' Subroutines
  
  multiply             shl x_var,#16              'get multiplicand into x[31..16]
                       mov t,#16                  'ready for 16 multiplier bits
                       shr y_var,#1 wc            'get initial multiplier bit into c
  :loop          if_c  add y_var,x_var wc         'if bit set, add multiplicand to product
                       rcr y_var,#1 wc            'put next multiplier in c, shift prod.
                       djnz t,#:loop              'loop until done                     
  multiply_ret         ret                        'return with product in y[31..0] 'this would be a subroutine
                       
  writer               wrlong y_var, varptr       'write the product from y[31..0] to the
  writer_ret           ret                        'product variable for the top object
  
  
  varptr               res   1                    'reserve space for cogregisters
  x_var                res   1
  y_var                res   1
  t                    res   1
  

  
  Andy
• pilot0315 Posts: 927

  2018-12-16 17:38

  Thanks for the help in cleaning it up. I will look at your suggestions. I will study it to see what I missed.
• pilot0315 Posts: 927

  2018-12-16 17:42

  BTW I get the cogid and cogstop to not leave the cog open.