Passing constants and addresses to assembler

Comments

• deSilva Posts: 2,967

  2007-09-26 21:44 edited 2007-09-26 21:44

  There is nothing to figure out
  - You can use constants "as is". They are fully integrated into the Propeller Tool concept.
  - You can set or preset any address you want in a DAT cell loaded up with the COG code. See the examples in my Tutorial.
• scotta Posts: 168

  2007-09-26 22:30 edited 2007-09-26 22:30

  The following code shows what I have been doing.
  
  I think its easier than using PAR, and uses the same code
  space and execution time (as PAR).
  
  Note how the LCDx_BAUD variable is being changed
  from spin (in Main method), on a separate cog. The
  assembler LCD object dereferences this on the fly.
  
  I have used this technique for simple assembler interfaces
  with 1 variable to 40 incoming references and
  (about) 10 pre-set constants.
  
  
  

  <
  *************************
  ****    MAIN.spin FILE   
  *************************
  OBJ
      LCD1     : "LCD"
      LCD2     : "LCD"
  
  VAR
      long LCD1_BAUD
      long LCD2_BAUD
  
  PUB Main
      LCD1_BAUD:=9600
      LCD2_BAUD:=19200
  
      LCD1.Start(1,@LCD1_BAUD)
      LCD2.Start(2,@LCD2_BAUD)
  
      repeat
           LCD1_BAUD:=LCD1_BAUD+10 
           LCD2_BAUD:=LCD2_BAUD+10
      
           DoMoreStuff(....)
  
  
  
  *************************
  ****    LCD.spin FILE   
  *************************
  PUB Setup(lcd_pin_, lcd_baud_)
    lcd_pin               := lcd_pin_             'copy constant to assembler space
    lcd_baud_ref      := lcd_baud_ref_     'copy reference to assembler space
    cognew(@Run, 0 )
   
  
  DAT ORG 0
  RUN
  'setup lcd_pin as a mask (note: lcd_pin is a constant and will never change)
       mov t1,#1
       shl   t1,lcd_pin
       mov lcd_pin,t1
  
  'read the baud rate, compute bit-ticks on the fly
       rdlong t1,lcd_baud_ref
       call #do_bit_ticks
  
  'more program
  ....
  
  
  t1 long 0
  lcd_pin long 0
  lcd_baud_ref long 0
  
  
        
  
  
  >
  
• deSilva Posts: 2,967

  2007-09-26 22:41 edited 2007-09-26 22:41

  Many people do it that way. Fine you give this additional example.
  
  I think "Start" = "SetUp" ?
  
  Edit: An additional advantage is that you can sometimes trade expensive COG space against cheap HUB space:
  

    lcd_pin               := |< lcd_pin_
  

  
  
  will save you 3 COG instructions..
  
  Post Edited (deSilva) : 9/26/2007 10:49:05 PM GMT
• scotta Posts: 168

  2007-09-26 22:53 edited 2007-09-26 22:53

  Parallax should do an example on this method, its
  much easier to read than:
  
  mov t1,par
  rdlong a,t1
  add t1,#4
  rdlong b,t1
  ...
• deSilva Posts: 2,967

  2007-09-26 23:01 edited 2007-09-26 23:01

  DeSilva did On page 11.
  
  But the PAR method is much more systematic and can have advantages in case of MANY parameters.
  Also, when you want to load many COGs with the same code a PAR parametrisation avoids the waiting for the end of loading of each of those COGs....
  
  The main pitfall is, that when using VAR variables as target, the mixing of LONGs, WORDs, and BYTEs can lead to much confusion
• scotta Posts: 168

  2007-09-26 23:31 edited 2007-09-26 23:31

  [noparse]:)[/noparse]
  
  I should Read the Funny Manual
  
  Thanks !