Subject:
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Re: D0 - D7
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Sun, 2 Mar 1997 16:58:46 GMT
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Original-From:
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Maria Pirsic <mpirsic@chat.carletonAVOIDSPAM.ca>
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Viewed:
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2227 times
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Mar,
This is what I've learned about the handyboard so far, and hopefully it
will give you a little insight into what's going on with D0-D7 (the
external bus).
Because of the way the handyboard is configured, it's operating in special
test mode. In special test mode there is a feature enabled called the
IRV. It's the Internal Read Visibility. This means that for all internal
reads, the data is driven onto the external bus. So just with an
oscilloscope you won't be able to get anything meaningful from D0-D7. The
IRV feature is meant to help debug the 68HC11, and you need to use a logic
analyzer to really see anything from those pins.
Maria
MAR ERICSON writes:
>
> I was poking about the HB with an osciloscope and ran into a bit of
> confusion. I had the motor outputs ON and wanted to see the PWM effect. I
> was able to see the square waves but...when I poked "behind" the octal
> latch to see what's going on with D0-D7, I got something I don't really
> understand. I got mostly a line at 5V and one at 0V. Setting the
> osciloscope to it's 100MHz max, I got what resembled a bunch of
> underdamped square waves overlapping eachother! Since the HC11 runs at
> 2MHz, I don't understand why this is happening or know whether I'm getting
> results that mean anything. Can someone explain what's happening?
> Thanks! :)
>
>
> -----------
> ericson mar
> Master of Engineering Candidate
> Project: Mobile Robotics
> mar@cooper.edu
>
> Department of Mechanical Engineering
> The Cooper Union for the Advancement of Science and Art
> -------------------------------------------------------
----------------------------------------------------------------------
Maria Pirsic
IEEE Branch Treasurer 96/97
Carleton University
mpirsic@chat.carleton.ca
----------------------------------------------------------------------
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