6502 bugs ???

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Article #20646

#20646

From: Morten Tolboel
Date: Thu, 02 Feb 1989 14:41

46 lines
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Are there any known bugs in the Rockwell 6502A microprocessor?

I am currently constructing a timer using the 6502 but there is
a problem I can't fix :

Program structure :

MAINPROGRAM - SUBRUTINES - INTERRUPTRUTINE - MORE SUB's - TABLES (data)

When I finaly got the program running I tried adding two NOP's before
the IRQ-routine, and the program worked ok. Then I added one more NOP
and the program died (after aprox. 1/2 sec.). If I added 256 NOP's
(or more than aprox. 180) the program worked ok again. 

If the NOP's are added after the IRQ-routine there are no problem at all.

Are there any page-shift bugs (or other problems) that could cause this
problem ????

PLEASE MAIL......

-------------------------------------!--------------------------
Kind regards                         ! JUB TVJOJA MAJD
Morten Tolboel                       ! all you ruskies !
Institute of electronic systems      ! 
University of Aalborg                !      \-/\-/
Denmark (not a suburb of Sweden!)    !      < F3 >
                                     !      /-\/-\
Mail: tolboel.iesd.dk                ! 
  or  tolboel.iesd.uucp              ! PRO REGE ET GREGE
  or  {...}!mcvax!dkuug!iesd!tolboel !  
-------------------------------------!--------------------------

-- 

-------------------------------------!--------------------------
Kind regards                         ! JUB TVJOJA MAJD
Morten Tolboel                       ! all you ruskies !
Institute of electronic systems      ! 
University of Aalborg                !      \-/\-/
Denmark (not a suburb of Sweden!)    !      < F3 >
                                     !      /-\/-\
Mail: tolboel.iesd.dk                ! 
  or  tolboel.iesd.uucp              ! PRO REGE ET GREGE
  or  {...}!mcvax!dkuug!iesd!tolboel !  
-------------------------------------!--------------------------

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!unmvax!pprg.unm.edu!hc!ames!amdcad!sun!pitstop!sundc!seismo!uunet!mcvax!kth!enea!dkuug!iesd!tolboel
From: tolboel@iesd.uucp (Morten Tolboel)
Newsgroups: sci.electronics
Subject: 6502 bugs ???
Message-ID: <1281@iesd.uucp>
Date: 2 Feb 89 14:41:02 GMT
Reply-To: tolboel@iesd.dk (Morten Tolboel)
Organization: Dept. of Comp. Sci., Aalborg University, Denmark
Lines: 46