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28

Different terminals didn’t (and don’t) use different kernel-level drivers. In Unix-style systems, the kernel does provide some terminal-related features, called line disciplines and the TTY layer which you mention; there is typically at least a raw line discipline (which doesn’t perform any translation), and a cooked line discipline (which provides more-or-...


13

In DOS, I remember being able to start COMMAND.COM on a COM port simply by doing this: REM Set COM1 speed and settings MODE COM1:38400,N,8,1 REM Hand over control to COM1! COMMAND COM1 REM The remote typed "exit"... You could then use a remote terminal connected to COM1 to give DOS commands on that machine - and simply type exit to return the machine ...


13

The RS232 routines in the ROM of the C64 use port B of the CIA (PB0-PB7 on the userport) to input/output all RS232 signals including Tx and Rx. So these routines don't actually use the shift register capabilities of the CIA, and have to do the shifting, parity calculation and bit-banging in software. That's the reason the speed is limited to about 1200 bps. ...


12

Looks like inverse polarity. The CR code is 015, 00001101 in binary. The codes for "=" and "y" are 075 and 171, 00111101 and 01111001 respectively. Note the sequence of four zeros in CR, and sequences of four ones in "=" and "y". With the inverse polarity, the character boundaries will depend on the speed with which they are sent because the start and the ...


12

In the early seventies, companies like HP and Wang sold 'programmable desktop calculators' that were really personal computers Not really, as they stood firmly on the calculator side. If at all, systems like the Cogar 4 and Datapoint 2200 are the origin of desktop computing. Complete units with a CPU, mass storage, CRT display and a full figured typewriter ...


11

DECnet is more of a protocol suite than a physical hardware standard. So asking what kind of physical connector it uses is kind of like asking what kind of physical connector TCP/IP uses -- the answer is, it uses whatever connector you need to use for the particular data link layer you're running DECnet on top of. If you are running DECnet over Ethernet, ...


11

This was not done by a “driver” at the OS level as you are thinking of it. In Unix, there were drivers that dealt with the RS232 interface and these were surfaced as /dev/tty* devices and dealt with things like speed, echo, etc. As for escape sequences controlling the display of the terminal, that is not done at the “driver” level as you are thinking of it....


10

The de facto – and indeed de jure – standard interface for computers controlling random equipment was RS-232. Some would argue with that, at least in certain industries — Hewlett-Packard’s HPIB (GPIB, IEE-488) was (and is) also commonly used to connect control and/or measurement equipment. It is simpler to implement than RS-232. So some early programmable ...


9

"It depends". I'm answering this in the context of DEC timesharing systems, since that's the natural habitat of a DEC VT100. There's a hardware device such as a DZ11 terminal multiplexer (8 lines) that controls terminal lines by some physical protocol, such as RS232 or 20mA current loop. The physical protocol is a matter for the hardware. But the OS needs ...


9

I thought the RS-232 port on the Vic-20 was completely separate from the cartridge port, so a thing had to be plugged into one or the other, and if the modem was plugged into the latter then it could not use the former. What am I missing? Or better what is mixed up. The device (Serial IEC) bus is often called a serial port, but that one was driven by VIA#2 ...


9

I think your best bet is an RS232-USB interface (NB I'm nor recommending the particular one linked, it was just the first one that came up in my search). Plug it in to your R-Pi's USB port and it should appear as a device in /dev. You should be able to then read and write to it like a file (well, you might not be able to write to it if your scale is only set ...


8

Unfortunately, Hercules plug, while being the same DE-9 plug/socket as "small" RS232, is completely electrically incompatible - other than using the same connector type, there is absolutely nothing in common between the two interfaces. You can damage the card, monitor or RS232 port/converter if you try connecting RS232 with the Hercules port. So, ...


8

In the early eighties, use of a 9-pin port for serial communications was uncommon. Most systems used the standard 25-pin port. I think it was IBM that made the 9-pin serial port popular, but I don't think that happened until around the time of the IBM PC AT (the original Macintosh also had a 9-pin serial port but it was wired differently, and was ...


8

RS-232 became "standard peripheral interface" later, when most of these "peripheral devices" adopted microprocessors. In early days, parallel ports were more common because they: can read-write data from logic elements like latches and d-triggers can control state of output triggers and even relays Actually they were a window to real life for CPU's ...


7

If the printer is offering an actual RS232 port, this should be identifiable by there being an RS232 level converter IC near the connector on its logic board: Usually, there will be a DS232/MAX232 or other MAX23x series IC, or a NEC D4711/UPD4711, or a combination of any of MC1488/MC1489/SN75188/SN75189/GD75189/GD75188/GD75232... This chip inverts the ...


7

According to the IBM PS/1 Technical Reference Manual, the pin assignment of the serial port is: So to answer your question: no, there is neither a second port nor a secondary channel for the first port. All the secondary lines are not connected.


6

DB25 in its very early stage provided for a secondary port on the same connector (using pins 12,13,14,16,19). Since then, those secondary and other additional signals became obsolete and even DB25 ports only use up to 9 signals - same as on in DB9 connector. It is possible that your motherboard provides another port and you would need to provide a cable ...


6

Not an Atari joystick. The Atari joystick was basically just a set of mechanical switches and each of the pins was either ground, +5 volts, or one of the switches. Were you designing a joystick back in the 80's to plug in to a serial port, you would have needed to put some electronics in it i.e. a chip to support RS232. I think that would have been ...


6

Yes, there were such gadgets that converted serial to parallel. The attached picture shows a Miracle Serial to parallel converter for the Sinclair QL, courtesy of 1984. The QL had no ex-factory Centronics printer interface, and solutions that blocked the expansion port for connecting a printer only were not really what customers wanted, so the Centronics ...


5

If you mean the original Hercules graphics card (picture further up), it had a video port and a parallel printer port. Neither can be connected to a RS-232 serial port in a sensible way. And even if you could, there's no way you can simulate a graphics card over an RS-232 connection: The graphics card can be only controlled via the ISA bus. If you want to ...


5

Two more slightly different situations from the past (well, everything in Retrocomputing is from the past...): 3270 Emulation When I was at the University of Maryland, College Park in the early 1980s, there were some Vaxes, a Univac 1100/80 and some other non-IBM large systems, and there were some micros (my first networking course was on the then brand new ...


5

This is only barely Retrocomputing. Almost all the printers I use today (and most people I know) are connected USB or networked. But ports for PCs are still available and as noted below, the companies I dealt with years ago for converters still sell them. But there aren't so many printers these days with serial or parallel ports now that 100M (or even 1G) ...


5

This can be done with a UART such as the 6402. Here's an example that converts serial to parallel:- Schematics of a Printer Adaptor Unlike more modern UARTs the 6402 does not have any internal registers that need to be 'programmed' to set it up, so it can be used standalone - and it has separate parallel read and write ports which are easier to use in a '...


4

As you surmised, a local loopback is your best diagnostic - and as you have mentioned, it avoids any interoperability issues with newer devices' "best effort" at RS-232 communication. As also described though, to be sure you've got a good connection you also need to add hardware signals, which means looping back output signals into inputs. A complete local ...


4

In addition to things the other answers have mentioned, in the early days of data communication the main channel was sometimes half duplex because the electronics weren't up to more, but there was a secondary channel at a much slower data rate and this line in the RS232 cable was used to control it. BTW, the kind of numbers I'm talking about are a high ...


4

I guess that's a field one can come up with many views - and all presented answers so far give a valid view with lots of additional information. This is intended to break it down to a more general statements: No, at the core no OS offers terminal drivers. Just serial (or whatever) line drivers handling bare communication to a device connected. Input (and ...


3

You want TcpSerSharp. This is a program that allows you to map a COM port to an outbound internet connection. You can download it at: https://github.com/sharpninja/tcpsersharp/releases The installer may error out due to not having windows services available. If it does, let me know and I'll send you a binary you can run from Command Line to start the ...


3

The only information I found so far is about Telebit modems where the secondary channel was used to query modem status while the primary channel was busy with data. This link reports an email from Telebit staff on configuration guides and mentions several supported machines - although there is no mention of secondary channel it's likely that some of those ...


3

As already stated, the question misses the point of what DECNet is. This is a common misconception regarding networks. DECNet sits at the Transport and Network levels of the OSI model of networking. The physical connector is only relevant at the Physical or Data Link levels. I used DECNet extesively for several years, on Thick-wire, Thin-wire, Optical, ...


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