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47

A UART (Universal Asynchronous Receiver-Transmitter) is a particular kind of hardware device that uses digital sampling to convert serial data that uses embedded start and stop bits for synchronization into and from parallel data. Not all forms serial communication use start and stop bits, and not all devices that use this form of serial communication uses ...


40

Five-bit teletypewriter codes ("Baudot", etc.) As far back as the early 1900s (believe it or not) there were teletypewriters. They were intended to replace Morse-style telegraphy, directly printing hardcopy rather than requiring an operator to listen to the Morse code and transcribe the messages by hand. The first successful such equipment was invented by ...


20

Simply, a UART is a serial port, but a serial port is not neccessary a UART. Serial port is a general term for anything serial, without further specification, while a UART defines a tranceiver for a specific asynchronus format. That Ports using asynchronus protocols like RS232 ot TTY are colloquially simplified as serial port shouldn't promote technical ...


19

The pre-ADB Macintoshes use a simple quadrature-encoded mouse input, no formal serial protocol. Quadrature encoding is a simple, physical process, that lends itself to a convenient cheat if you're synthesising input. Picture a cog, with an optical sensor pointing through the grooves. If you observed the digital output of that sensor, you'd be able to tell ...


16

The Baudot code uses 5 bits, and IIRC at least one of the mechanical teleprinters needed 1.5 stop bits to provide the time for the mechanism to do its thing, this at 45 baud. RTTY radio comms is probably the one place you still see this stuff in use. 9 bit on the other hand is semi common in RS485 industrial controllers.


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

Traditional Teletypes and many paper tape storage systems use these. You won't be able to read reels of punched paper tape if you drop support for 5 bit data. Nor will you be able to interface with Colossus systems, or the Lorentz communications they were designed to decode. At least one of each is apparently still in service - as a museum piece. Full ...


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 ...


9

It would be useful to establish whether anyone knows of any application for these which is still in service. RTTY (FSK modem over radio) still uses 5 bit code at low bitrates 45/50. It's often still used for automatic weather reports. What were the legacy applications for 5 or 6 bit serial data, and do any of them still exist? The six bit code was ...


9

Some sort of comms program that supports Zmodem on the 286 end and use "sz" to send from the unix end. Zmodem has some advantages in that usually the receiving computer will auto start reception of a file when it sees a Zmodem start sequence (there's a random number handshake to stop spoofing) The reason for recommending Zmodem is means you don't need to ...


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

I successfully got the RK-P400C printing from a serial console (minicom on Linux) today. Here's how to do it for future reference...;) The DB25 connector on the right side is a 25 pin serial port. At the top right of the typewriter there are sets of switches to select font and size, at the far right of those are two switches with the labels "KBI, KBII, EXT" ...


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

By the time I got my first analog modem, around 1980, my experience was the same as yours. Even and odd parity on 7-bit data was available, but almost all the BBSs featured 8N1. (The modems even still supported 5- and 6-bit data streams.) Apparently noise on phone lines by that time was so low that parity detection was considered superfluous for a large ...


7

You can also use dosbox or dosemu to run a simulated DOS environment, give it access to whatever ttyS* or ttyUSB* you have, and then use the DOS-to-DOS transfer methods. Personally, I prefer Laplink, which offers a convenient Norton-Commander like interface for file transfer. It can also bootstrap via the CTTY command on the remote computer, which is handy ...


6

Many many years ago, I interfaced an old IBM Selectric Terminal to my CPM machine. It used a 6 bit code that was not supported by my hardware and a 134.5 bit per second data rate also not supported. I wound up bit banging the data out with a software UART. Lucky for me, I was not interested in getting data from the Keyboard as that would have been much more ...


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

Is it text? In that case just pipe it from COMx into a file. Otherwise get some simple terminal program like @RossRidge already suggested. Or maybe Kermit. Kermit is a great start if you really want to start from scratch on the PC side since you may really bootstrap with a few lines of code. Or use BASIC to write your own receiving program :) Might be a real ...


6

According to this site, the 3481 uses the 3270 protocol, which isn't that difficult to parse and process, but definitely not dumb. I have seen "middleman" applications that allow to use a 3270-type terminal to interact with other applications (e.g. z/OS UNIX) which expect dumb terminals, but usage is quite different from what one is used to. It shouldn't be ...


6

It is possible, but not simple. The ordinary boot process which brings a working machine up from cold to the prompt for a Workbench disk doesn't offer an opportunity to drop into the debugger. A dodgy and potentially hardware-damaging approach is to cause an unexpected CPU exception by e.g. wiggling the trapdoor memory in an A500 -- execbase disappearing is ...


5

Parity is a "one-bit checksum over a single character". It can be used to detect single-bit errors in a serial asynchronous link (As the checksum is only one bit, two or more bits/char failed transmission can go undetected). Parity "even" adds a bit so that the sum of all data bits in the byte frame is even, while "odd" parity does the same so that the sum ...


5

UART is an initialism for "Universal Asynchronous Receiver/Transmitter", the manufacturer's name for the 8250 that was used in the original PC (and elsewhere) to run the serial port. That initialism continued to be used when labelling the 16550 which succeeded the 8250 and the term has attached itself to the serial port ever since.


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

Most (though not quite all) Android devices support operating the USB port as a USB host, either triggered by the usual OTG role pin on an adapter cable or by vendor-unique software setting. There can be various complex interactions with charging and ability to supply power to a peripheral, but for a low consumption device like a USB serial converter it ...


4

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, no, ...


4

This has already been well answered, but I wanted to respond with a couple of bootstrap solutions: that is, if all you have is a Linux box connected to a DOS box via a null-modem cable. minicom on Linux includes the ascii-xfr program. It's used as the default text file transfer protocol. By using its [-l linedelay] and [-c characterdelay] options it can be ...


4

Materials Needed Some other device (probably a computer) which we shall call "the terminal" to connect to your old device. On DOS or Windows, the device file for serial devices are called COM1 through COM4. On Unix/Linux systems, they in the form /dev/serial*, /dev/tty*, or /dev/ttyS*. You can use the following command to discover the names of your ...


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 ...


3

That chip is an ASIX MCS9820, as seen on a (current) StarTech 1 Port PCI RS232 Serial Adapter Card with 16550 UART. While it contains UART functions, the chip itself is a PCI→Serial bridge. The chip emulates a National Semiconductor 16550 UART, itself an improved version of the NS 8250 found in the IBM PC. 8-bit computers often had a Motorola 6850 or MOS ...


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