Hello Daniel,
There are many ways to implement Address Decoding with the
65xx family. The '138' decoder just might be the most popular of
the implementations.
I would like to suggest looking for a couple of used books which
can help you debunk some of the myths about address decoding
and other not so obvious hardware arrangements that you sometimes see when looking at 65xx designs.
They are :
'Programming & Interfacing the 6502 with experiments'
by Marvin L. DeJong
Blacksburg press, 1980
ISBN 79-67130
' Introduction to 6800/68000 MicroProcessors'
by Frederick F. Driscoll
PWS Publishers, 1987
ISBN 0-534-07692-0
- Although this book is targeted at the 6800/68000 the 6800 is
close enough to the 6502 that it is still relevant. This book also
gives an excellent explanation as to why we gate Phase2 with
R/W. ( Which you will see alot )
And Lastly :
' MicroProcessor Systems Engineering '
by R.C.Camp, T.A.Smay, C.J.Triska
Matrix Publishers, 1978
ISBN 0-916460-26-6
- Believe it or not this book is readily availible through Used_Book
networks. It treats the 8080,6800 & 6502. And does an
engineering review of the AIM-65 by Rockwell which used to be
a popular development platform for the 6502.
Although I would suggest getting all them, any one of these will
answer your present & future questions. Plus you will have a tangible reference.
Try looking for these through
www.alibris.com, I have had very
good luck with them, with NO problems.
Good Luck & Stay with it !
-Wally