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

What's wrong with this code?
 

  mov     W,#$1F   ;Set Mode to 1Fh to set direction bits
  mov M,W
  mov !rd,#0   ;Set ports D and E direction OUT
  mov !re,#0


  clr GTmpL   ;Use these to waste some time

  clr GTmpH
  mov GTemp,128


  clr re

  mov w,#$0F   ;Move them down again.  All bits have been toggled once
  mov rd,W


s4  decsz GTmpL
  jmp     s4 


  clc    ;inner loop should take 21.3 us
  snb re.5  ;rotate RE.5 to RD.0 and through RD and RE
  stc

  rl rd 
  rl re

  decsz GTmpH
  jmp s4

 

It is supposed to walk a pattern of four 1s through RD and the first six bits of RE.

The pattern goes through RD, but never gets to RE.  I tried placing a NOP between the two rl commands--it did no good

I modified the code to do the shifting in variables, as shown below and it worked fine.

 

  bank TaskBank
  clrb FSR.7
  mov w,#$0F
  mov rd,W
  mov PatternL,w  ;Set up fast walking pattern to toggle pins
  clr PatternH
s4  decsz GTmpL
  jmp     s4 
  clc    
  snb PatternH.5  ;rotate RE.5 to RD.0 and through RD and RE
  stc    

  rl PatternL 
  mov rd,PatternL
  rl PatternH
  mov re,PatternH
  decsz GTmpH
  jmp s4

 

So why can rl get a carry out of RAM, but not out of a port?  Or is it failing to put the carry in RE?

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=181670

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2007 (http://www.dotNetBB.com)