In SX Microcontrollers, SX/B Compiler and SX-Key Tool, PJMonty wrote:

SailorMan,

One thing to keep in mind is that the assembly in the first post was machine generated by the SX/B compiler.  Machine generated assembly code is harder for humans to read since it doesn't make human comprehension a priority.  I have gone through with a plain old text editor and done a search and replace to convert the unfriendly variable names with human friendly versions.  There are two things to notice here:

1 - Just changing variables names to something with meaning makes assembly code easier to read.

2 - ALWAYS use good variables names (such as "PwmCount") and not weak variable names (such as "Count" or "Cnt" or "C" to make the code easier to comprehend at a glance.

Here's the easier to read version:

[code]INTERRUPT
 
ASM
                                  ' ** Setup variables
 MOV NumBitsPerPort,#4            ' (2) Number of bits per port
 MOV BitOn_OrMask,#1              ' (2) OR Mask for turning a bit ON
 MOV BitOff_AndMask,#254          ' (2) AND Mask for turning a bit OFF
 INC PWM_Count                    ' (1) Adjust the PWM count 
                                  '     If the PWM value for each channel is
                                  '     less than PWM_Count then it should
                                  '     be high, othewise it should be low
 MOV PwmCount_Global,PWM_Count    ' (2) Make copy of PWM_Count in global memory
 MOV FSR,#PWM_Values              ' (2) Set FSR to address of 1st element of PWM values
:NEXT_BIT
  CJA IND,PwmCount_Global,@:MAKE_HIGH_B  ' (5/7) If this element is above PWM_Count
                                         ' Then jump to MAKE_HIGH_B
  AND RB,BitOff_AndMask                  ' (2) Value is below or equal to PWM_Count so
                                  '      make it low.
  JMP @:DONE_BIT_B                ' (4) Jump over MAKE_HIGH code
:MAKE_HIGH_B
  OR RB,BitOn_OrMask              ' (2) Value is above PWM_Count so make it HIGH
  NOP                             ' (1) Waste time
  NOP                             ' (1) Waste time
:DONE_BIT_B
  STC                             ' (1) Need to shift a 1 into AND mask value
  RL BitOff_AndMask               ' (1) Shift AND mask value
  CLC                             ' (1) Need to shift a 0 into OR mask value
  RL BitOn_OrMask                 ' (1) Shift OR mask value
  INC FSR                         ' (1) Point to next array element
 DJNZ NumBitsPerPort,@:NEXT_BIT   ' (3/5) Repeat until done
ENDASM
 
ReturnInt[/code]


BTW, you can make this even easier to read by copying it into the SX-Key IDE or any text editor that uses a non-proportional font.  That will makes the comments line up correctly.

[list]Thanks,
PeterM[/list]

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