Hi Folks,

I am working on some code that uses PortB interrupt on  change feature.
 I know that
bit test are dangerous because of the read-modify-write sequence.  A few
weeks ago, I remember seeing a list of instructions that did not use
read-modify-write.  Now I cannot locate the list in the data books.
  Target device is 16C621.

Question 1:  Can anyone point we to the list?

Question 2:   Does the plain vanilla move instruction do a
read-modify-write?


Question 3:  What about   movf  portB,w ; retrieve a copy of PortB to W
     movwf  temp  ; save the copy in temp
     btfss  temp,7  ; test if Bit 7 of Port B is set
  Will this keep PortB from getting screwed up?


Thanks for your help.

 ---- Steve