quartz/content/notes/06-6809-programming.md

title	aliases	tags
06-6809-programming		lecture cosc204

difficult

• no variables
• GOTO not loops
• only compare ints and bytes
• not really routines
• all vars global
• case sensitive

Hello World

• need a routine that given a string will print each chracter one at a time
• need to know how to print

Routines

routine:
	rts

• no params
• no local vars

calling routine

• lbsr, bsr, jsr
• very subtle differences
• we use bsr (branch to subroutine)

bsr routine

Interation

use GOTOs

	clra           //A = 0
more:
	cmpa #$06      //compare A to $06
	beq done       //if equal, branch to done
	inca           //increment a
	bra more       //branch to more
done:

• comparison only compares and sets flags in CC
• you then branch on the result
  • beq bge etc
• other intructions set flags to
  • lda etc
• so

lda $45
beq somewhere

6809.uk text screen