[Color Computer] Re: [Coco] 6809 Test and Set instruction?

[James Diffendaffer]

>You know, it might be possible to accomplish the equivalent of a 
>"test-and-set" as used for synching between cpus assuming to 6809s have 
>the logic as described above implemented. Suppose the following:
>
>FLAG	FCB $FF	* used for synchronization
>
>LOCK	INC FLAG
>	BEQ LOCKED	##
>	DEC FLAG	##
>	BRA LOCK
>LOCKED	* DO STUFF
>
>UNLOCK	DEC FLAG

I believe that's exactly what the article I posted the link too was
proposing.

Quote from the article (notice #2):
--------------------
It finally dawned on me that what I wanted was a dirt cheap, commonly
available, 8-bit microprocessor, like a Z80 or 6809. And while
designing tentative bus arbitration circuits for the 16-bit micros, I
realized that I really didn't need special multiprocessor support from
the CPU! I now claim that I can parallel any CPU that:

1. can "stretch" its memory cycle to accommodate slow memory, i.e.,
has a READY or WAIT input;

2. has some direct memory modify instruction, such as ROR M or INC M. 
--------------------








------------------------ Yahoo! Groups Sponsor --------------------~--> 
Great things are happening at Yahoo! Groups.  See the new email design.
http://us.click.yahoo.com/TISQkA/hOaOAA/yQLSAA/CFFolB/TM
--------------------------------------------------------------------~-> 

Brought to you by the 6809, the 6803 and their cousins! 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/ColorComputer/

<*> To unsubscribe from this group, send an email to:
    ColorComputer-unsubscribe at yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/