6 ms·

RS-232 defines the levels, the different signals, and the physical connectors. However, baud rate, parity, stop bits, and the like are at a "level" above RS-232

RS-232 defines the levels, the different signals, and the physical connectors. However, baud rate, parity, stop bits, and the like are at a "level" above RS-232, and so outside its scope.

jcrawfordor 2y ago
We also have to bear in mind that the computer industry often uses "RS-232" in reference to something that uses neither the connector nor the signaling levels defined by RS-232, something we have IBM to thank for.
- metaphor 2y ago
  > ...something we have IBM to thank for. Egregious rent seeking grifters at TIA demanding $165 per half-assed scanned copy[1] of a near 3-decade-old document that they couldn't even be bothered to properly OCR, and somehow IBM gets to shoulder the blame for the interoperability clusterfuck that ensued as everyone and their mother was profiting off their innovation? Oh, come off it. [1] https://store.accuristech.com/tia/standards/tia-tia-232-f?product_id=2594289 https://store.accuristech.com/tia/standards/tia-tia-232-f?pr...
  - mschuster91 2y ago
    Yet another fine example showing why standards should be at least readable to everyone for free, eh? The general public at large already pays huge amounts of money to various standardization organizations, be it ISO, IEC, DIN, UL, whatever. The resulting works should be public domain, similar to patents.
cwillu 2y ago
Also number of bits per byte.
wrs 2y ago
Does that framing even have a real official name? It’s usually handwaved around as “async serial” or “UART”. And remember, with whatever it’s called, in addition to sending characters of various bit lengths, you can send a “break”.
- auxym 2y ago
  It's called UART, to the best of my knowledge.
- formerly_proven 2y ago
  There is no standard for this. UARTs are called universal because they can be configured to work with "any" asynchronous serial protocol (within their bounds), which usually means - 1 start bit - 5-9 data bits - even or odd parity - 1-2 or sometimes 3 stop bits per frame. Hardware UARTs also typically oversample 16x, which is why simple software UARTs are often somewhat glitchy.
  - actionfromafar 2y ago
    The 5 bit data frame proved useful in the lab at uni where one of our tasks were to build a routable network over serial. :) Split each byte in 4-bit nibbles and used the remaining data bit for not-quite-in-band-signalling.
  - wrs 2y ago
    See, you called it “asynchronous serial protocol” there. But one can certainly think of asynchronous serial protocols that are outside those bounds. The Wikipedia article [0] calls this category “asynchronous start-stop signaling” but has no source. I guess the best term is “UART protocol”, despite the limited size of the “universe”, since it’s really just a de facto convention established by decades of chips called “UARTs”. [0] https://en.wikipedia.org/wiki/Asynchronous_serial_communication https://en.wikipedia.org/wiki/Asynchronous_serial_communicat...
- kjs3 2y ago
  UART refers to the chip that implements the framing. There are many different framings that can be implemented by a UART. Many of them have names.

RS-232 defines the levels, the different signals, and the physical connectors. However, baud rate, parity, stop bits, and the like are at a "level" above RS-232, and so outside its scope.

jcrawfordor 2y ago

We also have to bear in mind that the computer industry often uses "RS-232" in reference to something that uses neither the connector nor the signaling levels defined by RS-232, something we have IBM to thank for.

metaphor 2y ago
> ...something we have IBM to thank for. Egregious rent seeking grifters at TIA demanding $165 per half-assed scanned copy[1] of a near 3-decade-old document that they couldn't even be bothered to properly OCR, and somehow IBM gets to shoulder the blame for the interoperability clusterfuck that ensued as everyone and their mother was profiting off their innovation? Oh, come off it. [1] https://store.accuristech.com/tia/standards/tia-tia-232-f?product_id=2594289 https://store.accuristech.com/tia/standards/tia-tia-232-f?pr...
- mschuster91 2y ago
  Yet another fine example showing why standards should be at least readable to everyone for free, eh? The general public at large already pays huge amounts of money to various standardization organizations, be it ISO, IEC, DIN, UL, whatever. The resulting works should be public domain, similar to patents.

cwillu 2y ago

Also number of bits per byte.

wrs 2y ago

Does that framing even have a real official name? It’s usually handwaved around as “async serial” or “UART”. And remember, with whatever it’s called, in addition to sending characters of various bit lengths, you can send a “break”.

auxym 2y ago
It's called UART, to the best of my knowledge.
formerly_proven 2y ago
There is no standard for this. UARTs are called universal because they can be configured to work with "any" asynchronous serial protocol (within their bounds), which usually means - 1 start bit - 5-9 data bits - even or odd parity - 1-2 or sometimes 3 stop bits per frame. Hardware UARTs also typically oversample 16x, which is why simple software UARTs are often somewhat glitchy.
- actionfromafar 2y ago
  The 5 bit data frame proved useful in the lab at uni where one of our tasks were to build a routable network over serial. :) Split each byte in 4-bit nibbles and used the remaining data bit for not-quite-in-band-signalling.
- wrs 2y ago
  See, you called it “asynchronous serial protocol” there. But one can certainly think of asynchronous serial protocols that are outside those bounds. The Wikipedia article [0] calls this category “asynchronous start-stop signaling” but has no source. I guess the best term is “UART protocol”, despite the limited size of the “universe”, since it’s really just a de facto convention established by decades of chips called “UARTs”. [0] https://en.wikipedia.org/wiki/Asynchronous_serial_communication https://en.wikipedia.org/wiki/Asynchronous_serial_communicat...
kjs3 2y ago
UART refers to the chip that implements the framing. There are many different framings that can be implemented by a UART. Many of them have names.