Xref: utzoo comp.os.os9:888 comp.sys.m6809:1207 Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!ww0n+ From: ww0n+@andrew.cmu.edu (Walter Lloyd Wimer III) Newsgroups: comp.os.os9,comp.sys.m6809 Subject: Re: Single Stepping a 6809 Message-ID: Date: 28 Mar 90 04:04:34 GMT References: <4269@harrier.ukc.ac.uk>, <1990Mar27.022018.8981@agate.berkeley.edu> Organization: Network Development, Carnegie Mellon, Pittsburgh, PA Lines: 35 In-Reply-To: <1990Mar27.022018.8981@agate.berkeley.edu> Excerpts from netnews.comp.os.os9: 27-Mar-90 Re: Single Stepping a 6809 Philip Brown@headcrash.B (439) > What you do is get a hold of Tandy's Edtasm+, and take a look at their ZBUG > code (Using ZBUG, incidentally!). ZBUG porvides the userthe ability to > single-step through any ML routine, using the "," command directive > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * > Philip Brown pbrown@ocf.berkeley.edu > "I'm living on borrowed RAM" - Jon Aldrich > *********************************************** ZBUG accomplishes single stepping by replacing the next instruction with an SWI instruction (breakpoint) right before continuing execution. This might fill the bill or it might not. Obviously you can't use this mechanism to single-step through ROM routines. The hardware approach is certainly the ultimate in control and flexibility. (If I knew the details on how to get hardware single-stepping to work, I'd gladly post them; I could probably figure it out given the Motorola docs and enough time, but. . . . Hmmm, since you're supposed to be guaranteed execution of one instruction before an interrupt vector is taken, perhaps just tying, say, the NMI line to E would work. . . Then just execute an RTI each time you want to single step to the next instruction. There might be problems with trying to single-step through regular IRQ interrupt-handlers, though. . . ) ZBUG is a pretty decent debug monitor, though, by the way. Good luck, Walt Wimer