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DPLIB CLA ASM code need explanations

andrei markovits
Prodigy 30 points
Other Parts Discussed in Thread: CONTROLSUITE

Hello,

The sample code from :

c:\ti\controlSUITE\development_kits\TMDSIACLEDCOMKIT_v1.1\IsoACLighting-F28035-PLC_CENA\IsoACLighting-DPL-CLA.asm

Has poor comments/explanations:

.if(INCR_BUILD = 2)
     ADCDRV_1ch_CLA 9
  ;ADCDRV_1ch_CLA 2
  CNTL_2P2Z_CLA 1
  
  .ref _tsPtrCLA
  MI16TOF32  MR0, @_tsPtrCLA
  MADDF32  MR0, #1.0, MR0
  MF32TOI16   MR1, MR0
  
  MCMPF32  MR0, #2.0
  MMOV16  @_tsPtrCLA, MR1      
  MNOP      
  MNOP      
  MBCNDD   TS2_CLA, EQ  ;compare done
  MNOP      ;will happen regardless of branch result
  MNOP      ;will happen regardless of branch result
  MNOP      ;will happen regardless of branch result
  MCMPF32  MR0, #4.0  ;branch done
  MNOP
  MNOP
  MNOP
  MBCNDD   TS4_CLA, EQ  ;compare done
  MNOP      ;will happen regardless of branch result
  MNOP      ;will happen regardless of branch result
  MNOP      ;will happen regardless of branch result
  MCMPF32  MR0, #6.0  ;branch done
  MNOP
  MNOP
  MNOP
  MBCNDD   TS6_CLA, EQ  ;compare done
  MNOP      ;will happen regardless of branch result    
  MMOVF32   MR1,#0.0L  ;will happen regardless of branch result
  MF32TOI16 MR1,MR1   ;will happen regardless of branch result
  MBCNDD   TS_END, UNCF ;branch done, did not take branch, so leave ISR
  MNOP
  MNOP
  MNOP
    
TS2_CLA:
  ADCDRV_1ch_CLA 10
  ADCDRV_1ch_CLA 11
  CNTL_2P2Z_CLA 2

...

Question1:

Please give me a detailed explanation of the role of variable tsPtrCLA?

Question2:

Can you indicate, please, a documentation/application note about "tips and tricks" for writting CLA code in ASM language?

Thanks,

Andrei

  • 0
    TI__Guru 57255 points

    Hi Andrei,

    1) tsPtrCLA is used to time slice the ISR so that only certain tasks are run each ISR - the LLC control loop should run every ISR, each LED control loop only runs 1:6 ISRs.  This was done because it was decided that the LED lighting power stages did not require as much control bandwidth.

    Because the PWM update macro always contains the PWM updates for two control loops, we chose not to further separate the tasks.

    See below for a rough flowchart. 




    2) I don't know that a 'tips and tricks' document exists for writing in CLA assembly.  At the time that this project was developed, the C-compiler for the CLA had not been released.  Now that it is has, it is simpler and often just as efficient to write your code for the CLA in C. 
    (obviously if someone is good at writing assembly, one can still find more efficiency using assembly - but you have to still spend some time to do better than the compiler)

    If writing CLA code in assembly, I would note a few things:
    1) as seen in the TMDSIACLEDCOMKIT code, doing a comparison or a branch takes time.  If you construct your code carefully, it may be possible to complete useful instructions in the delay slots.
    2) There are CLA instructions to do things like add and move in parallel.  It is advantageous to use these, if possible, for obvious reasons.
    3) The following guide will give more details on the CLA - section 5 and 6 will be quite helpful.
    http://www.ti.com/lit/spruge6

    Hopefully this helps!


    Thank you,
    Brett

  • 0 in reply to Brett Larimore
    Prodigy 30 points
    Hello Brett,

    Flow chart completly answer my 1st question.

    Regarding 2nd question, now I have a good explanation why is so hard to find DPLIB examples in CLA ASM (for new projects they have been completely removed from TI samples code and replaced by CLA in C code... ).

    Quote:
    "At the time that this project was developed, the C-compiler for the CLA had not been released. Now that it is has, it is simpler and often just as efficient to write your code for the CLA in C."


    Thanks,
    Andrei