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Is there a Hex Keypad standard?

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  • ted_rossin
    I built an Elf from the Popular Electronics 1976 article back in 1978 and around 1979 I added a hex key pad in place of the binary interface (I used a
    Message 1 of 7 , Feb 1 11:56 AM
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      I built an Elf from the Popular Electronics 1976 article back in
      1978 and around 1979 I added a hex key pad in place of the binary
      interface (I used a solderless breadboard instead of the 8 switches
      for cost reasons).

      http://www.geocities.com/ted_rossin/Electronics/RCA/RCA.html

      Click on the picture for a larger view.

      My keypad is getting flakey and I'm thinking about a redesign and
      thought that if there is a standard then I should adhere to that.
      The following is a description of how my current keypad behaves.

      My keypad drives the INPUT switch after every 2nd key press. This
      also drives /EF4 and /DMA_IN low and drives 8-bit data onto the data
      bus in response to the ELF doing a Port 4 read. I think the INPUT
      to /EF4 and /DMA_IN and port 4 read is standard ELF behavior when
      the machine is in the LOAD state.

      I also have my keypad drive /EF3 low when any key is pressed
      and /EF4 low when the LOAD button is pressed. I have a toggle
      switch that selects between the LOAD button and the auto-load on
      every 2nd key press.

      This is my main user interface. Basically, I can look for EF3
      active and then read port 4 to see which key is pressed under
      program control or use the thing in auto-load mode to load programs
      starting at location zero. The later is how I jump to my monitor
      code that is held in ROM at location 0xf000.

      The keypad also has 8 LEDs connected to PORT 4 as I could not afford
      the HP hex displays back then.
    • Steve Valin
      Ted, Quest and Netronics followed the PopTronics article by using a 74C922/923 keyboard encoder, along with a set of latches (74C173 or similar). The 74C923
      Message 2 of 7 , Feb 1 2:01 PM
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        Ted,

        Quest and Netronics followed the PopTronics article by
        using a 74C922/923 keyboard encoder, along with a set
        of latches (74C173 or similar). The 74C923 encodes a
        keyboard press, has built in debounce, and presents
        the hex result on 4 or 5 lines, along with a strobe
        signal. The strobe is used to latch the previous
        value to give 8 bits. These two parts are isolated
        from the data bus via 4016 switches. The keyboard
        encoder is getting hard to find, but Jameco still
        sells them.

        The Elf II schematics can be found here:
        http://www.sbrune.com/COSMAC/ELF_II.pdf

        -steve

        --- ted_rossin <ted_rossin@...> wrote:

        > I built an Elf from the Popular Electronics 1976
        > article back in
        > 1978 and around 1979 I added a hex key pad in place
        > of the binary
        > interface (I used a solderless breadboard instead of
        > the 8 switches
        > for cost reasons).
        >
        >
        http://www.geocities.com/ted_rossin/Electronics/RCA/RCA.html
        >
        > Click on the picture for a larger view.
        >
        > My keypad is getting flakey and I'm thinking about a
        > redesign and
        > thought that if there is a standard then I should
        > adhere to that.
        > The following is a description of how my current
        > keypad behaves.
        >
        > My keypad drives the INPUT switch after every 2nd
        > key press. This
        > also drives /EF4 and /DMA_IN low and drives 8-bit
        > data onto the data
        > bus in response to the ELF doing a Port 4 read. I
        > think the INPUT
        > to /EF4 and /DMA_IN and port 4 read is standard ELF
        > behavior when
        > the machine is in the LOAD state.
        >
        > I also have my keypad drive /EF3 low when any key is
        > pressed
        > and /EF4 low when the LOAD button is pressed. I
        > have a toggle
        > switch that selects between the LOAD button and the
        > auto-load on
        > every 2nd key press.
        >
        > This is my main user interface. Basically, I can
        > look for EF3
        > active and then read port 4 to see which key is
        > pressed under
        > program control or use the thing in auto-load mode
        > to load programs
        > starting at location zero. The later is how I jump
        > to my monitor
        > code that is held in ROM at location 0xf000.
        >
        > The keypad also has 8 LEDs connected to PORT 4 as I
        > could not afford
        > the HP hex displays back then.
        >
        >





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      • ted_rossin
        From what I can see from the schematic there is no auto load feature like I built. So you have to key in two hex digits, then hit the INPUT switch in order to
        Message 3 of 7 , Feb 2 8:10 AM
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          From what I can see from the schematic there is no auto load feature
          like I built. So you have to key in two hex digits, then hit the
          INPUT switch in order to load a value. Also, the keypad strobe does
          not seem to be hooked up to any of the external flag lines.

          How do people use this keypad under program control? I use the
          keypad as arrow keys for a memory editor and screen grahics editor
          but fail to see how this could be done with a "standard" setup as it
          looks like I would be forced to change the code to work in an ugly
          way. For example, to move the cursor up, press the 8 key, then hit
          the INPUT key. Yuck.

          So, the bottom line is that my hex kepad is a superset of the
          standard in that I can sense when a key is pressed via the /EF3 line
          and I have an auto-load feature that saves a key press. The other
          bummer is that the keys on the Quest and Netronics boards are not
          organized the same way as my keypad which is set up like a modern PC
          keyboard so using 2,4,6 and 8 for arrow keys will be very confusing
          for others.

          --- In cosmacelf@yahoogroups.com, Steve Valin <sjvalin@...> wrote:
          >
          > Ted,
          >
          > Quest and Netronics followed the PopTronics article by
          > using a 74C922/923 keyboard encoder, along with a set
          > of latches (74C173 or similar). The 74C923 encodes a
          > keyboard press, has built in debounce, and presents
          > the hex result on 4 or 5 lines, along with a strobe
          > signal. The strobe is used to latch the previous
          > value to give 8 bits. These two parts are isolated
          > from the data bus via 4016 switches. The keyboard
          > encoder is getting hard to find, but Jameco still
          > sells them.
          >
          > The Elf II schematics can be found here:
          > http://www.sbrune.com/COSMAC/ELF_II.pdf
          >
          > -steve
          >
        • Dave Ruske
          Right you are. The Netronics hex keyboard had no way of telling you when a digit was pressed unless it happened to be different than the last two key presses.
          Message 4 of 7 , Feb 2 8:25 AM
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            Right you are. The Netronics hex keyboard had no way of telling you
            when a digit was pressed unless it happened to be different than the
            last two key presses. The VIP's keyboard was much handier in this
            regard; as I recall, it was a scanned keyboard that signaled when a
            key was pressed. An advantage to the scheme was that you could also
            tell when multiple keys were pressed. (Disclaimer: I'm not real
            familiar with the VIP, so my memory could be a bit off. I can look it
            up later if you're interested, though.)

            Dave


            On Feb 2, 2007, at 10:10 AM, ted_rossin wrote:
            > From what I can see from the schematic there is no auto load feature
            > like I built. So you have to key in two hex digits, then hit the
            > INPUT switch in order to load a value. Also, the keypad strobe does
            > not seem to be hooked up to any of the external flag lines.
            >
            > How do people use this keypad under program control? I use the
            > keypad as arrow keys for a memory editor and screen grahics editor
            > but fail to see how this could be done with a "standard" setup as it
            > looks like I would be forced to change the code to work in an ugly
            > way. For example, to move the cursor up, press the 8 key, then hit
            > the INPUT key. Yuck.
            >
            > So, the bottom line is that my hex kepad is a superset of the
            > standard in that I can sense when a key is pressed via the /EF3 line
            > and I have an auto-load feature that saves a key press. The other
            > bummer is that the keys on the Quest and Netronics boards are not
            > organized the same way as my keypad which is set up like a modern PC
            > keyboard so using 2,4,6 and 8 for arrow keys will be very confusing
            > for others.
            >



            [Non-text portions of this message have been removed]
          • ted_rossin
            I found the VIP schematics and see that they did something very similar to me in that they use /EF3 to detect a key press. Cool. My non-standard keyboard is
            Message 5 of 7 , Feb 2 9:26 AM
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              I found the VIP schematics and see that they did something very
              similar to me in that they use /EF3 to detect a key press. Cool. My
              non-standard keyboard is pretty much standard if the VIP is the
              standard.
            • Andrew Wasson
              Hey Ted, I for one like the Keypad auto load feature. I ve got an old ET3400A (heathkit) with that feature and it makes entering programs much easier. Also
              Message 6 of 7 , Feb 2 10:12 AM
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                Hey Ted,
                I for one like the Keypad auto load feature. I've got an old ET3400A
                (heathkit) with that feature and it makes entering programs much
                easier. Also the keypress detection feature is a nifty enhancement
                too. Nice work!

                These days with interfaces like Bob's general purpose I/O card or
                serial connections to the PC hex pads don't seem to draw that much
                attention however, I still don't mind keying in a page or two of HEX.

                Andrew


                --- In cosmacelf@yahoogroups.com, "ted_rossin" <ted_rossin@...> wrote:
                >
                > I found the VIP schematics and see that they did something very
                > similar to me in that they use /EF3 to detect a key press. Cool. My
                > non-standard keyboard is pretty much standard if the VIP is the
                > standard.
                >
              • Al W,
                I like the keypad auto load function too but one disadvantage if you happen to be clumsy like me is that mistakes are often costly time-wise. Some of the
                Message 7 of 7 , Feb 2 4:18 PM
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                  I like the keypad auto load function too but one disadvantage if you happen to be clumsy
                  like me is that mistakes are often costly time-wise. Some of the mentioned computers like
                  the ELF II require one to start from the bottom all over again and step back up to the error
                  byte.

                  On the VIP one can at least key in the error byte address to edit it directly. I copied the VIP
                  scheme on one of my home-built systems and it works very well for me.

                  When I implemented the auto-load function into my monitor program using a full-sized
                  ascii keyboard I provided special keys for backup one step and forward one step. Once
                  the monitor is active then editing memory in this fashion is much easier.

                  al winfrey
                  ....



                  --- In cosmacelf@yahoogroups.com, "Andrew Wasson" <andrew@...> wrote:
                  >
                  > Hey Ted,
                  > I for one like the Keypad auto load feature. I've got an old ET3400A
                  > (heathkit) with that feature and it makes entering programs much
                  > easier. Also the keypress detection feature is a nifty enhancement
                  > too. Nice work!
                  >
                  > These days with interfaces like Bob's general purpose I/O card or
                  > serial connections to the PC hex pads don't seem to draw that much
                  > attention however, I still don't mind keying in a page or two of HEX.
                  >
                  > Andrew
                  >
                  >
                  > --- In cosmacelf@yahoogroups.com, "ted_rossin" <ted_rossin@> wrote:
                  > >
                  > > I found the VIP schematics and see that they did something very
                  > > similar to me in that they use /EF3 to detect a key press. Cool. My
                  > > non-standard keyboard is pretty much standard if the VIP is the
                  > > standard.
                  > >
                  >
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