Martin J. Maney <PICLIST@MITVMA.MIT.EDU> wrote:

>     [.... a lot of good stuff that I'm too tired to respond to,
>     then.... ]
>
> mechanically adding a mask to register addresses to shut this up is
> likely to turn off the only diagnostic of a serious and
> easily-committed error [attempting to store a 9-bit value in an
> 8-bit register, etc.].

Martin:

If the masking is performed the way some people INSIST that it
should be done -- that is, by ANDing the value with 0x7F -- this is
true; the mask will force all values to 7 bits, and there will be no
indication that you've screwed up.

If, on the other hand, you "mask" the value by XORing it with 0x80,
attempts to store 9-bit values will still generate errors, as will
attempts to mask addresses that already ARE only 7 bits wide.

-Andy

Andrew Warren - fastfwd@ix.netcom.com
Fast Forward Engineering, Vista, California
http://www.geocities.com/SiliconValley/2499