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Thread: In-circuit CPU Emulator

  1. #1
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    Default In-circuit CPU Emulator

    I have to design-troubleshoot-implement a full blown in-circuit emulator (ICE)
    for Z80 cpu, and I have till tomorrow morning by 10 am...........NAAAAAAAA......

    The hardware device will sit in place of the Z80 and provides all capabilities of one.

    Would you please provide a detailed explanation on how one such ICE is generally
    implemented?


    ziloo

  2. #2
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    Quote Originally Posted by ziloo View Post
    Would you please provide a detailed explanation on how one such ICE is generally
    implemented?
    Have you ever written a software debugger for the Z80?
    Start with that, and add hardware to be able to overlay your debugger onto the target's memory space
    without interfering with either the target's I/O or memory.

    I doubt you will be able to do this in a day.

  3. #3
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    You could take a look at the manuals for the Applied Microsystems EM-180 as one example of how a Z-80 emulator operated and was built.

    http://www.bitsavers.org/test_equipm...ystems/EM_180/

  4. #4

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    You might try this https://www.ebay.com/itm/Z80-In-Circ...cAAOSwnDxUqF~c
    Something you could study or even build and see how well it works.

    Or if you need one there is https://www.ebay.com/itm/NICOLET-NIC....c100005.m2219

    Jim
    Who let out the magic smoke!!!!!!!!!!!

  5. #5
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    A cycle-correct ICE can be pretty daunting, even for something as simple as the Z80. For example, you must supply the DRAM refresh...

  6. #6
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    Quote Originally Posted by Al Kossow View Post
    I doubt you will be able to do this in a day.
    OMG!!!!

    I think my statement was taken way too seriously!!!!

    I have always wanted to know about the innards of a
    cycle-correct ICE. Is it like a continuous loop that
    provides the machine cycles at a group of nodes just
    like the actual CPU does?


    ziloo

  7. #7
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    At some point, ICEs began to be replaced by real CPUs with extra signals bonded out. I can remember those for the 80186 and 80286. It's almost always more reliable to use a real CPU with signals intercepted, than trying to emulate the behavior of one.

  8. #8
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    Quote Originally Posted by Chuck(G) View Post
    At some point, ICEs began to be replaced by real CPUs with extra signals bonded out. I can remember those for the 80186 and 80286. It's almost always more reliable to use a real CPU with signals intercepted, than trying to emulate the behavior of one.
    Back when I first started my professional firmware development career back in 2001 we were doing development on intel 8031 cores. We used a NOHAU ICE and it operated exactly like you say... a real 8031/51 was placed on a POD that plugged into the target. I wanna say they also made a Z80 based debugger, but I can't recall... at that time everything we did was intel. The pod attached to another ISA board and if you desired trace capability there was a separate board that provided the trace memory.

    It was a very useful thing, but also very finicky. The degree of finikiness depended on the target. Sometimes the system was so sensitive that from several feet away from the running target if I stood up from my desk it would reset. The JTAG debuggers are sooo much better these days.

  9. #9
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    Yup--typical one was a DIP plug connected to a box via some twisted Spectra-strip ribbon cable. The box had a CPU, with supplemental hardware to enable breakpoints, address tracking, and so on, connected to a larger box (terminal or development system). Are the schematics for Intel's ICE-80 in Bitsavers?



    Real gate-level simulation used to be the province of outfits like Zycad.
    Last edited by Chuck(G); November 17th, 2017 at 03:07 PM.

  10. #10
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    There were bond-out versions of some microprocessors in packages with extra pins which gave additional access to the internal operation of the microprocessor which was normally not available in the standard packages.

    For example this Intel C8051E in a 64-pin package. Without taking a look at the one I have to be sure I think that is the part that is used in the EMV-51 8051 emulator pod. I haven't found a datasheet anywhere for the Intel C8051E to see exactly how that part would be use in an emulator.


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