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In article <1990Aug31.000652.27385@monu6.cc.monash.edu.au> edp367s@monu6.cc.monash.edu.au (Rik Harris) writes:
>bbs00049@uafcseg.uucp (Red Roger) writes:

>>Hi i've seen some code that uses the ciab serial port set register. 
>>what is the real address of this register ??
>>bfd000 or bfd0fe - the reason i ask is that in the RKM h/w manual it says 
>>bfd000 yet this code works with it at bfd0fe 

>From the hardware point of view, it's quite possible that it works with
>any even address from $bfd000 to $bfd0fe (including $bfd002, $bfd004, etc).
>This could also be true for the other hardware registers in the $bf[de]xxx
>range.

However, you must always use the documented addresses for a register, if you
MUST directly use the register in the first place.  The register may appear
all over the place on an A1000, but only be in the specified location on an
A3000, for example.  There's no advantage to using the replicated image
addresses, unless you specifically want the program to fail on some systems.
If you use the documented addresses, they'll work as long as those particular
registers exist in a system.  Anything that can be done at the device rather
than register level should work forever, even if a future system replaces
those registers with something better and different.

>Rik Harris - Faculty of Computing and Information Technology,
 

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