dwight elvey dkelvey at
Sun Jun 1 13:28:25 CDT 2008

> From: dkelvey at> To: cctalk at> Date: Sun, 1 Jun 2008 10:06:41 -0700> Subject: RE: Introduction> > > > > > > From: lehmann at> >> > dwight elvey wrote:> >> >>> >> Hi> >> My German isn't that good. If the step rate is the problem,> >> I did see a couple routines that were creating steps. One> >> was RAMP.> >> Setting the controllers step rate is always done on just one> >> port. I forget which. All you should really need to do is find> >> all the out's to that port and set the step to the auto rate.> >> For my code, it was only in two places.> >> Dwight> >> > Hm - I'm not sure what "auto stepping" means. Normally, the controller> > sends a "step" signal (after the direction is set) to the harddrive and> > the harddrive responds with a "seek complete" signal - and the controller> > sends so many step signals and waits for the seek complete signal (before> > the controller sends the next step signal) until the wanted track is> > reached. That is how it works, or? So what is "auto step" here?> >> >> > Hi> All MFM drive will take steps at some particular rate. The st251 had what is> called auto stepping as well. In this mode, one could send the steps at a > very fast rate and the drive would save them into a counter. It would then> auto ramp the steps to a rate much faster than single steps could be done.> I think it use the highest order head address but I don't recall exactly> how this was done. A quick search on the web should find it.> Most of the newer MFM drives support autostepping and it is the perferred> stepping for these drives.> You do not need to do single step seeks for the steps as you state, you> just set the destination cylinder, direction and send steps at the rate specified> by the drive. You don't look for "seek complete" between steps, you just> send steps at the rate specified. When you believe you reached the desired> cylinder by the number of steps, you look for "seek complete" and not> before.> The ST251 can except controller rate stepping or auto stepping.> Dwight> 
 I looked it up. If the pulse for the step is less than 0.5ms it assume
the buffered or auto step. I was confusing compensation with the
head selects that also change with the ST412 standard.
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