Programming the Microprocessor

Use Notepad++ to write your source code.

Download and Install Notepad++ from https://notepad-plus-plus.org/
Open Notepad++ and select File and then select New. (Opens a new window)
Select Language and then select the Letter A then select Assembly. 
Select File again and then Save AS [enter a file name for your program] 
Make sure it has the .asm extension (yourfilename.asm) then click Save.
Make sure you have line numbering turned On. Found under Settings/Preferences/Editing/Display line number.  
Cut and paste the example code below into Notepad++ at line #1 
Select File again and then Save  

Example code:

      STX #$6ffc ; capture x reg
      LDX #$55    ; set counter to binary 10101010
count EQU *
      LDA #$0f   ; Turn on half of the LED's 00001111
      STA $6000  ; Write value to VIA chip
      DEX	 ; Decrease the X register by 1
      LDA #$f0   ; Turn on other half of the LED's 11110000
      BNE count
      LDX $6ffc  ; Restore X reg to orginal value
      LDA #$00   ; turn off all LED's 00000000
      STA $6000  ; Write value to VIA chip

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