Questions about IMSA 8080 - CP/M

This is a discussion on Questions about IMSA 8080 - CP/M ; I have some questions about the behavior of the original machine, which I can't figure out my self from the manual: When the machine is turned on, what do the programmed output LED's display? Random bits, all on/off? Are they ...

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  1. Questions about IMSA 8080

    I have some questions about the behavior of the original machine, which I
    can't figure out my self from the manual:

    When the machine is turned on, what do the programmed output LED's
    display? Random bits, all on/off? Are they set to a defined state with
    reset too?

    What is the second function of the reset switch labeled EXT. CLR.?

    What happens if the CPU is running and one raises the deposit switch? Is
    it locked while running, or will it put the data switch value at the
    current address into the running program? Similar, what happens if examine
    is raised, will it set the PC to the address of the address switches, or
    is it locked while running?

    Does the single step switch do the same in both positions?

    Thanks,
    Udo Munk
    --
    The real fun is building it and then using it...


  2. Re: Questions about IMSA 8080


    > When the machine is turned on, what do the programmed output LED's
    > display? Random bits, all on/off?

    * Mine are always all lit up.

    > Are they set to a defined state with reset too?

    * Reset doesn't change them.

    > What is the second function of the reset switch labeled EXT. CLR.?

    * That line is normally tied to the S-100 slave clear line. Never
    used.

    > What happens if the CPU is running and one raises the deposit switch? Is
    > it locked while running, or will it put the data switch value at the
    > current address into the running program?

    * Doesn't do anything.

    > Similar, what happens if examine
    > is raised, will it set the PC to the address of the address switches, or
    > is it locked while running?

    * You have to stop the machine first.

    > Does the single step switch do the same in both positions?

    * Yes, unless you change it like I did to have single step and slow
    step.

    JS

  3. Re: Questions about IMSA 8080


    "Udo Munk" wrote in message
    newsan.2008.09.21.10.54.01.498721@unix4fun.org...
    >I have some questions about the behavior of the original machine, which I
    > can't figure out my self from the manual:
    >
    > When the machine is turned on, what do the programmed output LED's
    > display? Random bits, all on/off? Are they set to a defined state with
    > reset too?
    >

    - RESET clears the outputs of the 8212 which drives the PROGRAMMED OUTPUT
    LEDs. Display is inverted, as the 8212's outputs are set LOW.

    > What is the second function of the reset switch labeled EXT. CLR.?
    >

    -This was an early idea to utilize an alternate EXTERNAL CLEAR line for
    boards which might have used such a feature. Seldom, if ever, used.

    > What happens if the CPU is running and one raises the deposit switch? Is
    > it locked while running, or will it put the data switch value at the
    > current address into the running program? Similar, what happens if examine
    > is raised, will it set the PC to the address of the address switches, or
    > is it locked while running?
    >

    -Function switches are disabled by the T5 line controlling the RESETs of the
    one-shots during RUN.

    > Does the single step switch do the same in both positions?
    >

    -Yes

    > Thanks,
    > Udo Munk
    > --
    > The real fun is building it and then using it...
    >




  4. Re: Questions about IMSA 8080

    On Mon, 22 Sep 2008 09:13:19 -0700, Thomas "Todd" Fischer wrote:

    >
    > "Udo Munk" wrote in message
    > newsan.2008.09.21.10.54.01.498721@unix4fun.org...
    >>I have some questions about the behavior of the original machine, which I
    >> can't figure out my self from the manual:
    >>
    >> When the machine is turned on, what do the programmed output LED's
    >> display? Random bits, all on/off? Are they set to a defined state with
    >> reset too?
    >>

    > - RESET clears the outputs of the 8212 which drives the PROGRAMMED OUTPUT
    > LEDs. Display is inverted, as the 8212's outputs are set LOW.


    Yes, I figured from the manual that the display is inverted and the
    programs from the users manual are running OK. I just couldn't figure out
    the initial state and if RESET is connected to the 8211.

    >> What is the second function of the reset switch labeled EXT. CLR.?
    >>

    > -This was an early idea to utilize an alternate EXTERNAL CLEAR line for
    > boards which might have used such a feature. Seldom, if ever, used.


    OK, so for a basic machine it can be ignored, when additional boards are
    used one has to figure if this boards make use of the line.

    >> What happens if the CPU is running and one raises the deposit switch?
    >> Is it locked while running, or will it put the data switch value at the
    >> current address into the running program? Similar, what happens if
    >> examine is raised, will it set the PC to the address of the address
    >> switches, or is it locked while running?
    >>

    > -Function switches are disabled by the T5 line controlling the RESETs of
    > the one-shots during RUN.


    I hoped so ;-) While working on the emulation I found out that it is no
    good to insert bytes into a running instruction of course, so I got this
    right already.

    >> Does the single step switch do the same in both positions?
    >>

    > -Yes


    Maybe I should get the schematics for the machine and print it sometime...
    many thanks for your answers.

    Udo Munk
    --
    The real fun is building it and then using it...


  5. Re: Questions about IMSA 8080

    On Mon, 22 Sep 2008 09:08:17 -0700, MdntTrain wrote:

    >> When the machine is turned on, what do the programmed output LED's
    >> display? Random bits, all on/off?

    > * Mine are always all lit up.


    OK.

    >> Are they set to a defined state with reset too?

    > * Reset doesn't change them.


    Not if they are all lit already. Since the reset line is connected to the
    8212 they should be all lit again after a reset, if I understood it right.

    >> What is the second function of the reset switch labeled EXT. CLR.?

    > * That line is normally tied to the S-100 slave clear line. Never used.


    OK, I'll ignore it for the basic machine for now.

    >> What happens if the CPU is running and one raises the deposit switch?
    >> Is it locked while running, or will it put the data switch value at the
    >> current address into the running program?

    > * Doesn't do anything.


    Good, I hoped so.

    >> Similar, what happens if examine
    >> is raised, will it set the PC to the address of the address switches,
    >> or is it locked while running?

    > * You have to stop the machine first.


    Good too.

    >> Does the single step switch do the same in both positions?

    > * Yes, unless you change it like I did to have single step and slow
    > step.


    I'm trying to emulate the original machine as close as possible, so I have
    implemented both positions to do the same. As with the original one always
    can modify it of course.

    > JS


    Thanks,
    Udo Munk
    --
    The real fun is building it and then using it...


  6. Re: Questions about IMSA 8080


    "Udo Munk" wrote in message
    newsan.2008.09.22.18.29.57.367714@unix4fun.org...
    > On Mon, 22 Sep 2008 09:13:19 -0700, Thomas "Todd" Fischer wrote:
    >
    >>
    >> "Udo Munk" wrote in message
    >> newsan.2008.09.21.10.54.01.498721@unix4fun.org...
    >>>I have some questions about the behavior of the original machine, which I
    >>> can't figure out my self from the manual:

    (snip(

    > Maybe I should get the schematics for the machine and print it sometime...
    > many thanks for your answers.


    -Please note that the earlier CPA schematics did not reflect an Engineering
    Change Order (ECO, c. Feb. 1976) which addressed disabling of the one-shots
    during RUN operation. I have this documented on the imsai.net web site
    under SUPPORT, where this and other ECO's are addressed. The board
    modification entailed "blue wire mods" as the original artwork was not
    corrected due to more urgent engineering priorities at the time. The
    Fulcrum ripoff boards produced in 1980 and later did correct the problems
    and eliminated the need for "blue wires".

    Regards,

    -Thomas "Todd" Fischer



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