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The 1802 Elf and Serial EEPROMs

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  • jdrose_8_bit
    Hello, I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and
    Message 1 of 20 , Mar 3, 2013
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      Hello,

      I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.

      I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.

      Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?

      Sorry for the simpleton questions. I am basically new to the hardware side of computers.
    • Kevin
      The interface would practically be another computer. If the idea is to be able to swap out ROMs, you could program a microcontroller to be the interface. But,
      Message 2 of 20 , Mar 3, 2013
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        The interface would practically be another computer. If the idea is to be able to swap out ROMs, you could program a microcontroller to be the interface.

        But, if you're going to do that, why not make the microcontroller also be the ROM? Many uC's now have built-in flash and USB interfaces, thusyou could load data from a PC.


        --- In cosmacelf@yahoogroups.com, "jdrose_8_bit" <rarecoinbuyer@...> wrote:
        >
        > Hello,
        >
        > I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.
        >
        > I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.
        >
        > Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?
        >
        > Sorry for the simpleton questions. I am basically new to the hardware side of computers.
        >
      • jdrose_8_bit
        Just thought of something. Did not look at it closely but the Spaceship code may need RAM for variables and the stack. If so, perhaps it could be re-written so
        Message 3 of 20 , Mar 3, 2013
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          Just thought of something. Did not look at it closely but the Spaceship code may need RAM for variables and the stack. If so, perhaps it could be re-written so variables could be stored in the registers only.


          --- In cosmacelf@yahoogroups.com, "jdrose_8_bit" <rarecoinbuyer@...> wrote:
          >
          > Hello,
          >
          > I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.
          >
          > I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.
          >
          > Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?
          >
          > Sorry for the simpleton questions. I am basically new to the hardware side of computers.
          >
        • jdrose_8_bit
          ... * Yes. That is what I wanted to do. Have ROMs for various 256 byte programs for the Elf that I could swap in and out. I would not have any RAM for
          Message 4 of 20 , Mar 3, 2013
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            --- In cosmacelf@yahoogroups.com, "Kevin" <kriceslo@...> wrote:
            >
            > The interface would practically be another computer. If the idea is to be able to swap out ROMs, you could program a microcontroller to be the interface.
            >

            * Yes. That is what I wanted to do. Have ROMs for various 256 byte programs for the Elf that I could swap in and out. I would not have any RAM for variables so it might be too limiting.

            >
            > But, if you're going to do that, why not make the microcontroller also be the ROM? Many uC's now have built-in flash and USB interfaces, thusyou could load data from a PC.
            >

            * Yes. That is an alternative I had not thought of. Have 256 bytes of RAM that is accessible by 1802 that could be written to from a PC through the USB. That would be very convenient. Thank you.

            I am thinking out loud I guess.

            >
            >
            > --- In cosmacelf@yahoogroups.com, "jdrose_8_bit" <rarecoinbuyer@> wrote:
            > >
            > > Hello,
            > >
            > > I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.
            > >
            > > I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.
            > >
            > > Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?
            > >
            > > Sorry for the simpleton questions. I am basically new to the hardware side of computers.
            > >
            >
          • William Donnelly
            I would use one of the newer, larger ROMs available and only use the first 256K. You can tie all of the other address lines to ground . There are some
            Message 5 of 20 , Mar 3, 2013
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              I would use one of the newer, larger ROMs available and only use
              the first 256K. You can tie all of the other address lines to "ground".
              There are some electronic issues involved in that sometimes, like
              needing to use a resistor in-line. Electronics is one of my non-strong points.

              EEPROM's are nice because they can be re-programmed. Some of them
              can be programmed in place, and don't need an external "programmer".
              If you don't know a lot, then the easiest way might be the best.

              The way the current Spaceship program is written, it probably does need
              RAM to operate. I haven't looked at it in awhile. But you can change the
              memory address to be a higher block of memory, and have RAM in the
              bottom and ROM in the higher part with the image. Or, if you want the
              whole thing in ROM, you could make an "autoloader" pretty easy that
              loads the first 256 bytes of RAM from a ROM using the 1802's program
              loader functionality. That wouldn't be too hard.

              I need to get my act together and make my "punched card / paper tape"
              and/or "sense card / paper tape" readers so that loading programs for
              the 1802 is fairly quick and easy in a simple retro-ish style.

              – Bill
              _________________
              (\__/) This is Bunny.
              (='.'=) Copy and paste Bunny into your signature.
              (")_(") Help Bunny gain World Domination.

              Deviant Artwork.

              The Consortium of indies, Artistes, & Others • www.CiAOiFilm.net

              .¸¸.·´¯`·.¸¸.·´¯`·.¸.::::?   www.ChicoSkyWatch.org
                GeoEngineering • Aerosol Spraying • Toxic Aluminum in Rainwater

              ✈__✈ █ █ ▄   www.AE911Truth.org

              d71081f2e3459993710e8af1002d1e1e

              On 3/3/2013 9:45 AM, jdrose_8_bit wrote:
               

              Hello,

              I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.

              I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.

              Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?

              Sorry for the simpleton questions. I am basically new to the hardware side of computers.


            • David W. Schultz
              ... In the obsolete category I like the SEEQ 52B13H 2KX8 EEPROM. One of the first EEPROMs that came out and simple to program. If you insist on using just 256
              Message 6 of 20 , Mar 3, 2013
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                On 03/03/2013 11:45 AM, jdrose_8_bit wrote:
                > Or perhaps recommend
                > a 256 byte parallel EEPROM (current or obsolete)?
                >

                In the obsolete category I like the SEEQ 52B13H 2KX8 EEPROM. One of the
                first EEPROMs that came out and simple to program. If you insist on
                using just 256 bytes you can tie the extra address lines to whatever
                level you like.

                Google turns up a data sheet and I see some available at ebay.

                --
                David W. Schultz
                http://home.earthlink.net/~david.schultz
                Returned for Regrooving
              • jdrose_8_bit
                Hey, that is great. That should work. With the 1802 you are limited to 256 bytes without address latching. Keep it simple in the spirit of the PE Elf.
                Message 7 of 20 , Mar 3, 2013
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                  Hey, that is great. That should work.

                  With the 1802 you are limited to 256 bytes without address latching. Keep it simple in the spirit of the PE Elf.



                  --- In cosmacelf@yahoogroups.com, "David W. Schultz" <david.schultz@...> wrote:
                  >
                  > On 03/03/2013 11:45 AM, jdrose_8_bit wrote:
                  > > Or perhaps recommend
                  > > a 256 byte parallel EEPROM (current or obsolete)?
                  > >
                  >
                  > In the obsolete category I like the SEEQ 52B13H 2KX8 EEPROM. One of the
                  > first EEPROMs that came out and simple to program. If you insist on
                  > using just 256 bytes you can tie the extra address lines to whatever
                  > level you like.
                  >
                  > Google turns up a data sheet and I see some available at ebay.
                  >
                  > --
                  > David W. Schultz
                  > http://home.earthlink.net/~david.schultz
                  > Returned for Regrooving
                  >
                • ajparent1
                  ... Well several things... In PE style for the Elf, latching the address for more space was one of the simple things to do. so that can be settled. As to
                  Message 8 of 20 , Mar 3, 2013
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                    --- In cosmacelf@yahoogroups.com, "jdrose_8_bit" <rarecoinbuyer@...> wrote:
                    >
                    > Hello,
                    >
                    > I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.
                    >
                    > I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.
                    >
                    > Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?
                    >
                    > Sorry for the simpleton questions. I am basically new to the hardware side of computers.
                    >

                    Well several things... In PE style for the Elf, latching the address for more space was one of the simple things to do. so that can be settled.

                    As to serial EEproms, yes its doable. The yabut is that you need a program to do the bitbash IO and that would still have to be toggled in and isn't going to be super small. The output line would be Q and the input is one of the unused EF lines. If Q is used for terminal or
                    other then a output port could be configured and used.

                    I have interfaced those serial eproms to a lot of machines and I lean to the bigger (more bits) parts when I do as once you do the interface code size is a handy thing.

                    If you extend the address it's fairly easy to find 8k and larger parallel EEproms.

                    Allison
                  • jdrose_8_bit
                    That is very good thinking. Have 2101 RAM chips at 00h to FFh and ROM from 100h and up. Latch. Toggle a small program in to the 256 byte RAM to jump to
                    Message 9 of 20 , Mar 3, 2013
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                      That is very good thinking.

                      Have 2101 RAM chips at 00h to FFh and ROM from 100h and up. Latch.

                      Toggle a small program in to the 256 byte RAM to jump to (EEP)ROM at 100h that copies the Spaceship code back to RAM starting at 00h. Then RUN RAM again from 00h.

                      You could have many numerous 256 byte programs stored in a single 8K EEPROM.

                      Genius. I am learning alot about hardware from this groupsite. Thank you.

                      --- In cosmacelf@yahoogroups.com, William Donnelly <william@...> wrote:
                      >
                      > I would use one of the newer, larger ROMs available and only use
                      > the first 256 bytes. You can tie all of the other address lines to "ground".
                      > There are some electronic issues involved in that sometimes, like
                      > needing to use a resistor in-line. Electronics is one of my non-strong
                      > points.
                      >
                      > EEPROM's are nice because they can be re-programmed. Some of them
                      > can be programmed in place, and don't need an external "programmer".
                      > If you don't know a lot, then the easiest way might be the best.
                      >
                      > The way the current Spaceship program is written, it probably does need
                      > RAM to operate. I haven't looked at it in awhile. But you can change the
                      > memory address to be a higher block of memory, and have RAM in the
                      > bottom and ROM in the higher part with the image. Or, if you want the
                      > whole thing in ROM, you could make an "autoloader" pretty easy that
                      > loads the first 256 bytes of RAM from a ROM using the 1802's program
                      > loader functionality. That wouldn't be too hard.
                      >
                      > I need to get my act together and make my "punched card / paper tape"
                      > and/or "sense card / paper tape" readers so that loading programs for
                      > the 1802 is fairly quick and easy in a simple retro-ish style.
                      >
                      > -- Bill
                      > _________________
                      > (\__/) This is /Bunny/.
                      > (='.'=) Copy and paste /Bunny/ into your signature.
                      > (")_(") *Help /Bunny/ gain World Domination.*
                      >
                      > Deviant Art <http://popeyetheob.deviantart.com/gallery/>work.
                      >
                      > The Consortium of /indies/, Artistes, & Others . www.CiAOiFilm.net
                      > <http://www.CiAOiFilm.net/>
                      >
                      > .¸¸.·´¯`·.¸¸.·´¯`·.¸.::::? www.ChicoSkyWatch.org
                      > <http://www.ChicoSkyWatch.org/>
                      > GeoEngineering . Aerosol Spraying . Toxic Aluminum in Rainwater
                      >
                      > ?__? ? ? ? www.AE911Truth.org
                      >
                      > <http://www.AE911Truth.org/> d71081f2e3459993710e8af1002d1e1e
                      >
                      > On 3/3/2013 9:45 AM, jdrose_8_bit wrote:
                      > >
                      > > Hello,
                      > >
                      > > I am gathering the parts to build a PE type 1802 Elf for testing the
                      > > 1861 replacement circuit. Instead of manually toggling the Spaceship
                      > > code and bitmap into the Elf I would like to burn it into a 256 x 8
                      > > bit ROM of some sort.
                      > >
                      > > I cannot find any current parallel 256 byte EEPROMs but I have found
                      > > some serial EEPROMs like the Microchip 24LC02B-E/P. I think I
                      > > understand how they work. Plus they are very cheap and small.
                      > >
                      > > Would it be difficult or possible to use one of these 256 byte 8 pin
                      > > DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend
                      > > a 256 byte parallel EEPROM (current or obsolete)?
                      > >
                      > > Sorry for the simpleton questions. I am basically new to the hardware
                      > > side of computers.
                      > >
                      > >
                      >
                    • joshbensadon
                      Have you looked at my VELF project? I use an EPROM in high memory and RAM in low memory. If you start the system with the data switches set to 0x01 then it
                      Message 10 of 20 , Mar 3, 2013
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                        Have you looked at my VELF project? I use an EPROM in high memory and RAM in low memory. If you start the system with the data switches set to 0x01 then it loads the Enterprise Program into RAM and runs. Other switch settings load other programs. It has a hex keypad so it can operate as a VIP, but you can omit that circuitry.

                        The EPROM also has a monitor program that talks via RS232, allows you to upload programs from your PC through the EF2/Q line.





                        --- In cosmacelf@yahoogroups.com, "jdrose_8_bit" <rarecoinbuyer@...> wrote:
                        >
                        > That is very good thinking.
                        >
                        > Have 2101 RAM chips at 00h to FFh and ROM from 100h and up. Latch.
                        >
                        > Toggle a small program in to the 256 byte RAM to jump to (EEP)ROM at 100h that copies the Spaceship code back to RAM starting at 00h. Then RUN RAM again from 00h.
                        >
                        > You could have many numerous 256 byte programs stored in a single 8K EEPROM.
                        >
                        > Genius. I am learning alot about hardware from this groupsite. Thank you.
                        >
                        > --- In cosmacelf@yahoogroups.com, William Donnelly <william@> wrote:
                        > >
                        > > I would use one of the newer, larger ROMs available and only use
                        > > the first 256 bytes. You can tie all of the other address lines to "ground".
                        > > There are some electronic issues involved in that sometimes, like
                        > > needing to use a resistor in-line. Electronics is one of my non-strong
                        > > points.
                        > >
                        > > EEPROM's are nice because they can be re-programmed. Some of them
                        > > can be programmed in place, and don't need an external "programmer".
                        > > If you don't know a lot, then the easiest way might be the best.
                        > >
                        > > The way the current Spaceship program is written, it probably does need
                        > > RAM to operate. I haven't looked at it in awhile. But you can change the
                        > > memory address to be a higher block of memory, and have RAM in the
                        > > bottom and ROM in the higher part with the image. Or, if you want the
                        > > whole thing in ROM, you could make an "autoloader" pretty easy that
                        > > loads the first 256 bytes of RAM from a ROM using the 1802's program
                        > > loader functionality. That wouldn't be too hard.
                        > >
                        > > I need to get my act together and make my "punched card / paper tape"
                        > > and/or "sense card / paper tape" readers so that loading programs for
                        > > the 1802 is fairly quick and easy in a simple retro-ish style.
                        > >
                        > > -- Bill
                        > > _________________
                        > > (\__/) This is /Bunny/.
                        > > (='.'=) Copy and paste /Bunny/ into your signature.
                        > > (")_(") *Help /Bunny/ gain World Domination.*
                        > >
                        > > Deviant Art <http://popeyetheob.deviantart.com/gallery/>work.
                        > >
                        > > The Consortium of /indies/, Artistes, & Others . www.CiAOiFilm.net
                        > > <http://www.CiAOiFilm.net/>
                        > >
                        > > .¸¸.·´¯`·.¸¸.·´¯`·.¸.::::? www.ChicoSkyWatch.org
                        > > <http://www.ChicoSkyWatch.org/>
                        > > GeoEngineering . Aerosol Spraying . Toxic Aluminum in Rainwater
                        > >
                        > > ?__? ? ? ? www.AE911Truth.org
                        > >
                        > > <http://www.AE911Truth.org/> d71081f2e3459993710e8af1002d1e1e
                        > >
                        > > On 3/3/2013 9:45 AM, jdrose_8_bit wrote:
                        > > >
                        > > > Hello,
                        > > >
                        > > > I am gathering the parts to build a PE type 1802 Elf for testing the
                        > > > 1861 replacement circuit. Instead of manually toggling the Spaceship
                        > > > code and bitmap into the Elf I would like to burn it into a 256 x 8
                        > > > bit ROM of some sort.
                        > > >
                        > > > I cannot find any current parallel 256 byte EEPROMs but I have found
                        > > > some serial EEPROMs like the Microchip 24LC02B-E/P. I think I
                        > > > understand how they work. Plus they are very cheap and small.
                        > > >
                        > > > Would it be difficult or possible to use one of these 256 byte 8 pin
                        > > > DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend
                        > > > a 256 byte parallel EEPROM (current or obsolete)?
                        > > >
                        > > > Sorry for the simpleton questions. I am basically new to the hardware
                        > > > side of computers.
                        > > >
                        > > >
                        > >
                        >
                      • jdrose_8_bit
                        I have not. I will. Thank you.
                        Message 11 of 20 , Mar 3, 2013
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                          I have not. I will.

                          Thank you.

                          --- In cosmacelf@yahoo, "joshbensadon" wrote:
                          >
                          > Have you looked at my VELF project? I use an EPROM in high memory and RAM in low memory.
                          >
                        • Lee Hart
                          ... The easiest route is to get an EPROM programmer. There are hundreds of makes and models, new and used. Some require a PC or other computer to use them;
                          Message 12 of 20 , Mar 3, 2013
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                            On 3/3/2013 11:45 AM, jdrose_8_bit wrote:
                            > Instead of manually toggling the Spaceship code and bitmap into the
                            > Elf, I would like to burn it into a 256 x 8 bit ROM of some sort.

                            The easiest route is to get an EPROM programmer. There are hundreds of
                            makes and models, new and used. Some require a PC or other computer to
                            use them; others can also be used with their own keypad and display.

                            Some EPROMs (like the 2716) are ridiculously easy to program. You can
                            literally program them on a breadboard socket with switches on the
                            address and data lines, and a pushbutton to pulse the program pin.

                            The main drawback of EPROMs is that you need an ultraviolet light to
                            erase them. But again, these are common and cheap (especially used).

                            Now, on to EEPROMs... They are just like EPROMs, but can be electrically
                            erased as well as programmed. They come in parallel and serial versions.

                            Serial EEPROMs are very cheap. But you will need a program running on
                            the Elf to generate the clock and read the data from it. It's a small
                            program, but having to enter it kind of defeats the reason you wanted a
                            a ROM (so you don't have to type in programs manually).

                            So, a parallel EEPROM looks like a better option. If you get the right
                            ones, they too can be programmed with a cheap programmer or even
                            switches on a breadboard socket.

                            --
                            The most dangerous enemy of a better solution is an existing one that
                            is just good enough. -- Eric S. Raymond
                            --
                            Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
                          • jdrose_8_bit
                            I have a Batronics BX32P. It seems to be pretty flexible and will program a number of parallel EEPROMs that should work in the project. They are not as cheap
                            Message 13 of 20 , Mar 4, 2013
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                              I have a Batronics BX32P. It seems to be pretty flexible and will program a number of parallel EEPROMs that should work in the project. They are not as cheap as serial EEPROMs but are much more convenient to use.

                              Thanks to everyone for their help. A great learning experience.

                              --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@...> wrote:
                              >
                              > On 3/3/2013 11:45 AM, jdrose_8_bit wrote:
                              > > Instead of manually toggling the Spaceship code and bitmap into the
                              > > Elf, I would like to burn it into a 256 x 8 bit ROM of some sort.
                              >
                              > The easiest route is to get an EPROM programmer. There are hundreds of
                              > makes and models, new and used. Some require a PC or other computer to
                              > use them; others can also be used with their own keypad and display.
                              >
                              > Some EPROMs (like the 2716) are ridiculously easy to program. You can
                              > literally program them on a breadboard socket with switches on the
                              > address and data lines, and a pushbutton to pulse the program pin.
                              >
                              > The main drawback of EPROMs is that you need an ultraviolet light to
                              > erase them. But again, these are common and cheap (especially used).
                              >
                              > Now, on to EEPROMs... They are just like EPROMs, but can be electrically
                              > erased as well as programmed. They come in parallel and serial versions.
                              >
                              > Serial EEPROMs are very cheap. But you will need a program running on
                              > the Elf to generate the clock and read the data from it. It's a small
                              > program, but having to enter it kind of defeats the reason you wanted a
                              > a ROM (so you don't have to type in programs manually).
                              >
                              > So, a parallel EEPROM looks like a better option. If you get the right
                              > ones, they too can be programmed with a cheap programmer or even
                              > switches on a breadboard socket.
                              >
                              > --
                              > The most dangerous enemy of a better solution is an existing one that
                              > is just good enough. -- Eric S. Raymond
                              > --
                              > Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
                              >
                            • Lee Hart
                              ... Great! sounds like you re all set. PS: Jameco Electronics www.jameco.com is one good source of inexpensive parts. They have the 28C16 and other EEPROMs for
                              Message 14 of 20 , Mar 4, 2013
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                                On 3/4/2013 6:33 AM, jdrose_8_bit wrote:
                                > I have a Batronics BX32P. It seems to be pretty flexible and will
                                > program a number of parallel EEPROMs that should work in the
                                > project.

                                Great! sounds like you're all set. PS: Jameco Electronics www.jameco.com
                                is one good source of inexpensive parts. They have the 28C16 and other
                                EEPROMs for $3-$4.

                                --
                                Ingenuity gets you through times of no money better than money
                                will get you through times of no ingenuity. -- Terry Pratchett
                                --
                                Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
                              • jdrose_8_bit
                                ... Actually, I do not mind typing in programs. It is toggling in programs that has sorta lost it s novelty. :-) Also, I would like to be able to save any
                                Message 15 of 20 , Mar 8, 2013
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                                  --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@...> wrote:
                                  >
                                  > you will need a program running on
                                  > the Elf to generate the clock and read the data from it. It's a small
                                  > program, but having to enter it kind of defeats the reason you wanted a
                                  > a ROM (so you don't have to type in programs manually).
                                  >

                                  Actually, I do not mind typing in programs. It is toggling in programs that has sorta lost it's novelty. :-)

                                  Also, I would like to be able to save any programs that I develop for the PE ELF. Some sort of ROM seems like the simplest and most cost effective way to do it that the Elf can use directly.
                                • Lee Hart
                                  ... Well, that is a simple problem to solve. It just takes a few chips to provide a hex keypad for entry and hex LED display for output. The hex display was in
                                  Message 16 of 20 , Mar 8, 2013
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                                    On 3/8/2013 11:38 AM, jdrose_8_bit wrote:
                                    > Actually, I do not mind typing in programs. It is toggling in programs that has sorta lost it's novelty. :-)

                                    Well, that is a simple problem to solve. It just takes a few chips to
                                    provide a hex keypad for entry and hex LED display for output. The hex
                                    display was in the original Popular Electronics ELF articles, and
                                    variations of it were found in the Quest and Netronics ELF as well.

                                    The keypad circuit can be found in the Quest And Netronics ELF as well.
                                    it uses a 74C923 keyboard encoder chip.

                                    > Also, I would like to be able to save any programs that I develop for the PE ELF. Some sort of ROM seems like the simplest and most cost effective way to do it that the Elf can use directly.

                                    There are all the standard methods, of course. Send or receive data
                                    serially, using software and the Q/EF4 lines. Or add an EPROM or EEPROM
                                    programmer and loader; the hardware and software is minimal.

                                    Another option is simply to battery back up your RAM, so it simply
                                    retains the data as long as the batteries last. With CMOS, this can be
                                    many years!

                                    Finally, one I want to play with but haven't had time. RAMtron makes
                                    ferroelectric nonvolatile RAM chips. They work the same, and have the
                                    same pinouts as normal RAM chips, but are *nonvolatile*. No battery
                                    needed. :-)

                                    --
                                    An engineer can do for a nickel what any damn fool can do for a dollar.
                                    -- Henry Ford
                                    --
                                    Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
                                  • David W. Schultz
                                    ... Then perform a simple upgrade: 1) Add a CD4042 to latch 4 bits of address. 2) Replace the 22 pin sockets for the 2101 SRAMs with a pair of 24 pin sockets
                                    Message 17 of 20 , Mar 9, 2013
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                                      On 03/08/2013 11:38 AM, jdrose_8_bit wrote:
                                      > Actually, I do not mind typing in programs. It is toggling in
                                      > programs that has sorta lost it's novelty. :-)
                                      >
                                      > Also, I would like to be able to save any programs that I develop for
                                      > the PE ELF. Some sort of ROM seems like the simplest and most cost
                                      > effective way to do it that the Elf can use directly.
                                      >

                                      Then perform a simple upgrade:

                                      1) Add a CD4042 to latch 4 bits of address.
                                      2) Replace the 22 pin sockets for the 2101 SRAMs with a pair of 24 pin
                                      sockets wired for 6116 2KX8 SRAMs.

                                      Now you have a lot more memory to play with but more importantly, a
                                      non-volatile option. If I read the 28C16 datasheet from Jameco right, it
                                      is a drop in replacement for the 6116 and even better requires no extra
                                      hardware to program. Just leave it alone for a bit after strobing the
                                      write enable line.

                                      Now you have a couple of choices:

                                      1) Put the 28C16 in the low socket and program it using the load mode.
                                      2) Put it in the high socket and program using a simple program. Perhaps
                                      a variation on ETOPS.

                                      You might want to add a write protect jumper to the socket with the EEPROM.


                                      --
                                      David W. Schultz
                                      http://home.earthlink.net/~david.schultz
                                      Returned for Regrooving
                                    • jdrose_8_bit
                                      ... That is an interesting option. A CR2032 would probably be enough for a while. I am not much of an EE but I doubt that it would take a complicated circuit
                                      Message 18 of 20 , Mar 21, 2013
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                                        --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@...> wrote:
                                        >

                                        >
                                        > Another option is simply to battery back up your RAM, so it simply
                                        > retains the data as long as the batteries last. With CMOS, this can be
                                        > many years!
                                        >


                                        That is an interesting option. A CR2032 would probably be enough for a while. I am not much of an EE but I doubt that it would take a complicated circuit change to the PE ELF to do battery backup for the RAM.

                                        Relatively inexpensive way to go.
                                      • jdrose_8_bit
                                        ... I was able to find it. Thanks! http://www.incolor.com/bill_r/elf/html/elf-2-39.htm
                                        Message 19 of 20 , Mar 21, 2013
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                                          --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@...> wrote:

                                          >
                                          > Indeed, it was in one of their original articles.
                                          >

                                          I was able to find it. Thanks!
                                          http://www.incolor.com/bill_r/elf/html/elf-2-39.htm

                                          >The circuitry needed
                                          > is little more than the RAM, two diodes, and a pullup resistor on the
                                          > RAM's "write" pin so it won't accidentally float low.
                                          >
                                          > On the Membership Card, I found that I didn't even need the diodes. I
                                          > could battery backup *everything*, and still hold data for a year on two
                                          > AA cells.
                                          >
                                        • Lee Hart
                                          ... Indeed, it was in one of their original articles. The circuitry needed is little more than the RAM, two diodes, and a pullup resistor on the RAM s write
                                          Message 20 of 20 , Mar 21, 2013
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                                            On 3/21/2013 8:06 AM, jdrose_8_bit wrote:
                                            >> Another option is simply to battery back up your RAM, so it simply
                                            >> retains the data as long as the batteries last. With CMOS, this can be
                                            >> many years!

                                            > That is an interesting option. A CR2032 would probably be enough for a while. I am not much of an EE but I doubt that it would take a complicated circuit change to the PE ELF to do battery backup for the RAM.

                                            Indeed, it was in one of their original articles. The circuitry needed
                                            is little more than the RAM, two diodes, and a pullup resistor on the
                                            RAM's "write" pin so it won't accidentally float low.

                                            On the Membership Card, I found that I didn't even need the diodes. I
                                            could battery backup *everything*, and still hold data for a year on two
                                            AA cells.
                                            --
                                            Anyone can make the simple complicated. Creativity is making the
                                            complicated simple. -- Charles Mingus
                                            --
                                            Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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