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Re: 88-2SIO Hardware Handshaking Issues

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  • jack99rubin
    ... or ... Thanks Tom - I ve got nothing to add to that!! Have a great holiday weekend, all ye who lurk. Jack
    Message 1 of 9 , Jul 3, 2008
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      >
      > Mote: My RS-232 book has the following bit of Altair history:
      >
      > "Nothing in the world of microcomputers is more reviled, despised,
      or
      > misunderstood that the RS-232-C interface. Ordinary mild-mannered
      > humans are driven berserk by the experience of connecting their
      > computer equipment. Sometimes this rage gets out of hand:"
      >
      > "A dispute between a customer and a computer store over a $180 bill
      > has ended in tragedy with the fatal shooting of the store's owner.
      >
      > A 42-year-old man, Floyd French of Gladstone, Missouri, was arrested
      > at the scene and later charged with first-degree murder. The victim
      > was the owner of the Altair Computer Center, Henry Phillip Bouldin.
      > According to police, French had bought a computer from Bouldin, then
      > brought in a printer purchased elsewhere and asked that [the store]
      > make the two compatible..."
      > -- Infoworld, June 20, 1983.
      >

      Thanks Tom - I've got nothing to add to that!!
      Have a great holiday weekend, all ye who lurk.

      Jack
    • Alan Outhier
      OH! One of my hot buttons, I ll try to keep it short & simple. Hopefully, both devices are configured as DTEs (neither is a modem), and both devices are
      Message 2 of 9 , Jul 3, 2008
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        OH! One of my hot buttons, I'll try to keep it short & simple.

        Hopefully, both devices are configured as DTEs (neither is a modem),
        and both devices are equipped with male db25s (part of being
        configured as a DTE but some manufactures never understood that).

        Option 1 - buy a commercial null modem cable.

        Option 2 - build your own.
        pin 2 -> pin 3
        pin 3 -> pin 2
        pin 7 -> pin 7

        At each end jumper pins 6-8-20 ('hope I remember this correctly).

        Don' t try to implement hardware control, it won't buy you anything.

        There's two cents worth for free!

        Al


        At 01:07 PM 7/3/2008, jack99rubin wrote:

        > >
        > > Mote: My RS-232 book has the following bit of Altair history:
        > >
        > > "Nothing in the world of microcomputers is more reviled, despised,
        >or
        > > misunderstood that the RS-232-C interface. Ordinary mild-mannered
        > > humans are driven berserk by the experience of connecting their
        > > computer equipment. Sometimes this rage gets out of hand:"
        > >
        > > "A dispute between a customer and a computer store over a $180 bill
        > > has ended in tragedy with the fatal shooting of the store's owner.
        > >
        > > A 42-year-old man, Floyd French of Gladstone, Missouri, was arrested
        > > at the scene and later charged with first-degree murder. The victim
        > > was the owner of the Altair Computer Center, Henry Phillip Bouldin.
        > > According to police, French had bought a computer from Bouldin, then
        > > brought in a printer purchased elsewhere and asked that [the store]
        > > make the two compatible..."
        > > -- Infoworld, June 20, 1983.
        > >
        >
        >Thanks Tom - I've got nothing to add to that!!
        >Have a great holiday weekend, all ye who lurk.
        >
        >Jack
        >
        >
        >------------------------------------
        >
        >Yahoo! Groups Links
        >
        >
        >
      • Tom Sanderson
        ... I think this likely good advice, but since learning is part of the fun, I m trying to better understand handshaking and why it won t buy me anything. I m
        Message 3 of 9 , Jul 4, 2008
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          > Don' t try to implement hardware control, it won't buy you anything.

          I think this likely good advice, but since learning is part of the
          fun, I'm trying to better understand handshaking and why it won't buy
          me anything. I'm curious about the handshaking signals provided by
          the 2SIO and the short notes in the manual about some signals.

          I'm also curious about the effect of the Break Out Box LEDs on the
          symptoms. Even if I do not use hardware control, I need to learn how
          to use the Serial to Ethernet converter. The converter does seem to
          require CTS, but does not like RTS from the 2SIO. It is happy when
          CTS is not connected to the 2SIO.

          > Hopefully, both devices are configured as DTEs (neither is a
          modem),
          > and both devices are equipped with male db25s (part of being
          > configured as a DTE but some manufactures never understood that).

          The Ethernet converter is DTE and uses a 9-pin male connector. The
          2SIO is DCE and uses the proper female db25. I can work around the
          issue, but am still looking for a better understanding of the 2SIO
          CTS and the manual note about using it for DTR.

          I'd like to learn more about the following:

          ...found the following in
          the manual: NOTICE!! "If the Data Carrier Detect and Clear to Send
          inputs are not connected, they must be jumpered to Ground."

          I also found a handwritten note: "MITS manual was unclear in it's note
          to jumper DCD & CTS to GND. These signals must be jumpered to +5v at
          the interface connector because it gets inverted before it gets to the
          6850.

          Tom

          -- In altaircomputerclub@yahoogroups.com, Alan Outhier <aouthier@...>
          wrote:
          >
          > OH! One of my hot buttons, I'll try to keep it short & simple.
          >
          > Hopefully, both devices are configured as DTEs (neither is a
          modem),
          > and both devices are equipped with male db25s (part of being
          > configured as a DTE but some manufactures never understood that).
          >
          > Option 1 - buy a commercial null modem cable.
          >
          > Option 2 - build your own.
          > pin 2 -> pin 3
          > pin 3 -> pin 2
          > pin 7 -> pin 7
          >
          > At each end jumper pins 6-8-20 ('hope I remember this
          correctly).
          >
          > Don' t try to implement hardware control, it won't buy you anything.
          >
          > There's two cents worth for free!
          >
          > Al
          >
          >
          > At 01:07 PM 7/3/2008, jack99rubin wrote:
          >
          > > >
          > > > Mote: My RS-232 book has the following bit of Altair history:
          > > >
          > > > "Nothing in the world of microcomputers is more reviled,
          despised,
          > >or
          > > > misunderstood that the RS-232-C interface. Ordinary mild-
          mannered
          > > > humans are driven berserk by the experience of connecting their
          > > > computer equipment. Sometimes this rage gets out of hand:"
          > > >
          > > > "A dispute between a customer and a computer store over a $180
          bill
          > > > has ended in tragedy with the fatal shooting of the store's
          owner.
          > > >
          > > > A 42-year-old man, Floyd French of Gladstone, Missouri, was
          arrested
          > > > at the scene and later charged with first-degree murder. The
          victim
          > > > was the owner of the Altair Computer Center, Henry Phillip
          Bouldin.
          > > > According to police, French had bought a computer from Bouldin,
          then
          > > > brought in a printer purchased elsewhere and asked that [the
          store]
          > > > make the two compatible..."
          > > > -- Infoworld, June 20, 1983.
          > > >
          > >
          > >Thanks Tom - I've got nothing to add to that!!
          > >Have a great holiday weekend, all ye who lurk.
          > >
          > >Jack
          > >
          > >
          > >------------------------------------
          > >
          > >Yahoo! Groups Links
          > >
          > >
          > >
          >
        • Dan Roganti
          Tom Sanderson wrote: I m trying to understand the 88-2SIO RS-232 interface, especially RTS/CTS handshaking. There are some notes in the 2SIO manual that I
          Message 4 of 9 , Jul 4, 2008
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            Tom Sanderson wrote:
            I'm trying to understand the 88-2SIO RS-232 interface, especially
            RTS/CTS handshaking. There are some notes in the 2SIO manual that I
            don't quite understand and I'm seeing some strange symptoms when
            connecting to a Serial to Ethernet converter.
              
            This has always been a stickler
            Over the years, these are some things that I keep in mind and helps avoid the racking ones brains out :)
            I always pass it on wherever I go.
            (you'll find this in the various references to RS232)

            --There's only 6 kinds of combinations for RS232 cables--I used to memorize this.
            1. DTE - DTE: w/ Handshaking (signals always cross)
            2. DTE - DTE: w/ No Handshaking (loopback all handshake lines)
            3. DTE - DCE w/Handshaking (signals never cross)
            4. DTE - DCE w/No Handshaking (loopback all handshake lines)
            5. DTE - Peripheral:  such as a printer,papertape--still a DTE ,but Dumb Terminal Equip :)
                               This is where your info on CTS<-->DTR comes from
            6. Loopback tester -- this is a given

            --Hardware Handshaking are always software controlled, when it doubt, loop it back.
            Unless you have specific info from the docs explaining the timing of these signals, it's best to loopback them
            This helps prevent the software from getting confused :)
            This is wired on both ends --and always both sets, not just one set
            RTS<-->CTS
            DTR<-->DCD<-->DSR
            --DCE is only to communicate over a transport medium, such as, a phone line, T1 truck, fiber, cable, etc.
            Otherwise the other end is always a DTE, such as another computer,
            or your serial2ethernet or serial2usb (which connects to another computer)


            hope this helps,
            =Dan
            -- 
            [ Pittsburgh 250th --- http://www2.applegate.org/~ragooman/   ]



          • Alan Outhier
            ... First, what I m about to say is not without exception. With the proper software, hardware control could be useful, but I doubt that many will come up with
            Message 5 of 9 , Jul 7, 2008
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              At 12:16 AM 7/4/2008, you wrote:
              > Don' t try to implement hardware control, it won't buy you anything.

              I think this likely good advice, but since learning is part of the
              fun, I'm trying to better understand handshaking and why it won't buy
              me anything. I'm curious about the handshaking signals provided by
              the 2SIO and the short notes in the manual about some signals.

              First, what I'm about to say is not without exception. With the proper software, hardware control could be useful, but I doubt that many will come up with such system software for an old Altair machine.

              (Receive)..Unless you're running an interrupt driven serial port, your software polls for incoming data. When the data arrives, you're either ready for it or your not. If a second character arrives before you read the first, you lose that first character. This is called an overrun. It doesn't matter how the arrival of the new data is manifested, (receive data register full, or some other status bit - set by a control line change) your software does the same thing.

              Next point - your computer will have to tell the transmit device when it's not ready or not ready to receive. Wouldn't it be a lot easier just make sure it's ready (read in the last character)?

              More could be discussed here, but time doesn't permit.

              Al
            • Tom Sanderson
              RS-232 interfacing can be simple. Three wires allow me to use an ADM- 3a to boot and run Altair BASIC. ... machine. The only time I expect to encounter a
              Message 6 of 9 , Jul 7, 2008
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                RS-232 interfacing can be simple. Three wires allow me to use an ADM-
                3a to boot and run Altair BASIC.

                > First, what I'm about to say is not without exception. With the
                > proper software, hardware control could be useful, but I doubt that
                > many will come up with such system software for an old Altair
                machine.

                The only time I expect to encounter a interrupt driven serial port is
                with MITS Timesharing BASIC.

                An Altair can connect to Telex, Teletypes, printers, acoustic modems,
                external modems, CRT and paper terminals, USB converters, Ethernet
                Converters, other computers, and virtual hardware. The connection can
                wired, wireless, cellular, or Ethernet. That collection would include
                some non-standard devices and exceptions to general rules.

                Software encountered by an Altair includes: MITS software, CP/M
                software, internet protocols, Linux, Windows, Microsoft .Net, APE,
                virtual com ports, HyperTerminal, handshaking emulation...

                Some combinations of hardware and software will require special
                cables and some will require handshaking or some type. Before I make
                cables and worry about exceptions, I am questioning that capabilities
                of the 88-2SIO and Motorola 6850.

                To what extent can the 2SIO implement a "normal" RS-232
                connection? "Normal" is defined by a table in the 2SIO manual. Notes
                about DTR and RTS leave "normal" ambiguous.

                I believe my current issues with an Ethernet converter are related to
                disabling capabilities. My current application should work with three
                wires. For some reason the Ethernet converter requires CTS and does
                not like RTS from an Altair. Handshaking is disabled in the converter
                configuration. Using LEDs to check signal status will fix the
                symptoms. I believe a straight through connection should work. I'm in
                the area of exceptions and special cables, but don't understand why,

                I think we all agree that the need for Altair hardware handshaking is
                fairly rare and prone to problems. That leads me to question the
                proper 2SIO configuration when hardware handshaking is not used. The
                NOTICE!! in the 2SIO manual about DCD ant CTS leave 2SIO
                configuration ambiguous.

                The standard MITS 2SIO cable lacks DTR and is not "normal RS-232".
                What do we need to know for proper configuration of DTR and
                configuratiom DCD and CTS without handshaking?

                Tom

                --- In altaircomputerclub@yahoogroups.com, Alan Outhier
                <aouthier@...> wrote:
                >
                > At 12:16 AM 7/4/2008, you wrote:
                > > > Don' t try to implement hardware control, it won't buy you
                anything.
                > >
                > >I think this likely good advice, but since learning is part of the
                > >fun, I'm trying to better understand handshaking and why it won't
                buy
                > >me anything. I'm curious about the handshaking signals provided by
                > >the 2SIO and the short notes in the manual about some signals.
                >
                > First, what I'm about to say is not without exception. With the
                > proper software, hardware control could be useful, but I doubt that
                > many will come up with such system software for an old Altair
                machine.
                >
                > (Receive)..Unless you're running an interrupt driven serial port,
                > your software polls for incoming data. When the data arrives,
                you're
                > either ready for it or your not. If a second character arrives
                before
                > you read the first, you lose that first character. This is called
                an
                > overrun. It doesn't matter how the arrival of the new data is
                > manifested, (receive data register full, or some other status bit -
                > set by a control line change) your software does the same thing.
                >
                > Next point - your computer will have to tell the transmit device
                when
                > it's not ready or not ready to receive. Wouldn't it be a lot easier
                > just make sure it's ready (read in the last character)?
                >
                > More could be discussed here, but time doesn't permit.
                >
                > Al
                >
              • Craig Landrum
                ... Over the many years of working withg RS-232 I ve found the same thing. Some UART chips handle hardware flow control nicely if programmed to do so, but some
                Message 7 of 9 , Jul 8, 2008
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                  >>
                  >> Don' t try to implement hardware control, it won't buy you anything.
                  >>

                  Over the many years of working withg RS-232 I've found the same thing.
                  Some UART chips handle hardware flow control nicely if programmed to
                  do so, but some don't. I also tend to simply hardwire 4-5, 6-8-20 and
                  be done with it, and set up my dumb terminals for *software* flow
                  control using XON/XOFF, which most hosts recognize and most dumb
                  terminals support. It is often an option that you have to select
                  somehow on the the terminal, though.

                  FYI, XON and XOFF are ASCII control characters. XON (start sending
                  again) is cntl-Q / DC1 / 11Hex ; and the XOFF (stop sending) is
                  cntl-S / DC3 / 13Hex



                  --
                  Craig Landrum
                  Chief Technical Officer
                  mindwrap, inc.
                  Phone: (540) 675-3015 x 229
                  Fax: (540) 675-3130
                  email: craigl@...
                • Tom Sanderson
                  ... More questions for my list: How does the Motorola 6850 fit into this picture? The 6850 and Altair 2SIO have documented support for CTS, RTS, DCD, and DTR.
                  Message 8 of 9 , Jul 8, 2008
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                    > Some UART chips handle hardware flow control nicely if programmed to
                    > do so, but some don't. ......

                    More questions for my list:

                    How does the Motorola 6850 fit into this picture? The 6850 and Altair
                    2SIO have documented support for CTS, RTS, DCD, and DTR. I'm
                    wondering what works and what doesn't?

                    To what extent will a device find the Alatair a "standard"
                    or "normal" RS232 device?

                    If I program the Altair 2SIO to handle hardware flow control nicely,
                    what problems should I expect?

                    Tom

                    --- In altaircomputerclub@yahoogroups.com, Craig Landrum <craigl@...>
                    wrote:
                    >
                    > >>
                    > >> Don' t try to implement hardware control, it won't buy you
                    anything.
                    > >>
                    >
                    > Over the many years of working withg RS-232 I've found the same
                    thing.
                    > Some UART chips handle hardware flow control nicely if programmed to
                    > do so, but some don't. I also tend to simply hardwire 4-5, 6-8-20
                    and
                    > be done with it, and set up my dumb terminals for *software* flow
                    > control using XON/XOFF, which most hosts recognize and most dumb
                    > terminals support. It is often an option that you have to select
                    > somehow on the the terminal, though.
                    >
                    > FYI, XON and XOFF are ASCII control characters. XON (start sending
                    > again) is cntl-Q / DC1 / 11Hex ; and the XOFF (stop sending) is
                    > cntl-S / DC3 / 13Hex
                    >
                    >
                    >
                    > --
                    > Craig Landrum
                    > Chief Technical Officer
                    > mindwrap, inc.
                    > Phone: (540) 675-3015 x 229
                    > Fax: (540) 675-3130
                    > email: craigl@...
                    >
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