Passing Object output into assembly code

Comments

• JonnyMac Posts: 9,507

  2011-01-18 10:03 edited 2011-01-18 10:03

  It's not very difficult: the value you want to pass to a PASM routine is written to a hub variable that can be accessed from the PASM cog with rdlong. There are many objects that use this process to pick up a value from the hub. You PASM program only needs to know the hub address of the variable it is to read.
  
  Really simply... you can start a PASM cog pointing to the variable
  

  cognew(@entry, @myvar)
  

  
  The address of that variable (a long) is now in the par register and your PASM code can read it
  

  dat
  
                          org     0
  
  entry                   rdlong  tmp1, par                       ' read parameter
  
                          ' now do something with it
  

  
  This is just one variable. If you need to pass more then you'll pass the address of the first in a group and build and address list at the top of your PASM code.
• Mike Green Posts: 23,101

  2011-01-18 10:11 edited 2011-01-18 10:11

  The passing of values to a cog has to be designed into the code because the routine running in the cog has complete control and other cogs have no access to that cog's memory. Normally this is done through a location in hub memory and this is read using RDLONG / RDWORD / RDBYTE. It's really easy to read two values from hub memory. It's harder to figure out what to do with them. Usually attenuation is done by multiplication or division which has to be done by subroutine on the Propeller unless it's always in terms of powers of two. Changing the delay time depends on how the delay is handled.
• stephenwagner Posts: 147

  2011-01-19 08:13 edited 2011-01-19 08:13

  I am going to work some SPIN and PASM issues this weekend and post. Thanks for the tips.
  
  SJW
• Graham Stabler Posts: 2,510

  2011-01-19 08:45 edited 2011-01-19 08:45

  http://forums.parallax.com/showthread.php?94027-Assembly-step-by-step
  
  Steps 3 and 4 cover this sort of thing.
  
  Graham
• stephenwagner Posts: 147

  2011-01-24 05:10 edited 2011-01-24 05:10

  Thanks.
  
  I also found the Jan. 2011 Spin Zone to be very helpful.
  
  
  SJW