6809 SBC - test-drb@ccmp.vtda.org

31 Jan 2010

...
  Tony Duell wrote:
   Having
learned assembly language programming on the beautifully 
 simple architecture and instruction set of the 6800, the Byte magazine
 article linked to below that I read when it was originally published 
 really impressed me.? In the 6809 they made one of the earliest efforts 
 I know of to really tweak an already great uP instruction set based upon 
 an analysis of existing software:   
 I found the 6809 to be by far the nicest 8-bit CPU I ever worked with. 
 The instruction set was simple and very orthogonal, the fact that you had 
 various relative addressing modes meant you could write truely 
 position-independant code, there were 2 stack points, and so on. Unlike 
 certain chips I could name, there were no major misfeatures that I came 
 across.

 Of course the problem (as we all know) is that it came out too late. By 
 that tine everybody was using the Z80 or 6502. Oh well.

 It always suprised me that hre BBC micro used the 6502 rather than the 
 6809. By the time the Beeb was designed, Acorn had made a 6809 processor 
 board for their System machines, so they must have had experience with 
 the chip. THe Beeb is nice, but a Beeb with a 6809 processor would have 
 been something else :-)

 -tony
   When I moved from the 6800 to the 6809 (in assembly language - *many* 
 years ago) I was sort of astounded and at the same time very pleased by 
 the way many of the little subroutines I had written for the 6800 became 
 one instruction in the 6809.? I think it will always be my favorite 
 8-bit CPU.? My only annoyance at the time was the fact that there was no 
 way for the software to reset the companion UART chip, whose number I've 
 completely forgotten by now.? 6821 maybe???
 Later,
 Charlie Carothers 
I was so impressed I even took a photo of it.  A photo of the die of an Atmel EF6809CV is
a short way down my page here:

http://diephotos.blogspot.com/