Timeline for Why do articles use the term "UART" instead of "serial port"?
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 4 at 3:03 | comment | added | scruss | @JimMacKenzie - The Amiga 500's UART was part of the Paula custom chip | |
| Jan 3 at 22:27 | comment | added | Michael Karcher | @JimMacKenzie Standard PC UARTs originally did not have a significant buffer (except for holding one byte while the next one is received / the previous one is transmitted). The 16-character buffer to reduce the odds of characters getting dropped was introduced with the 3rd generation of UARTs (the 16550, after the 16450 and the 8250), and was usually called "FIFO". | |
| Sep 24, 2022 at 21:09 | comment | added | supercat | @Tommy: How much difficulty would there have been synchronizing the CB1 input on the VIC-20 with the rising edge of phi1, thus making the hardware feature usable? | |
| Nov 15, 2017 at 2:55 | history | edited | Tommy | CC BY-SA 3.0 | Corrected as per Jerry Coffin's comment. |
| Nov 14, 2017 at 17:45 | comment | added | Tommy | ... and for the record, since it seems to be leading to a lot of debate: my answer doesn't say that serial ports must have UART chips; my first comment expands in response to somebody else making the converse explicit by stating the chips through which serial ports are connected on some other machines, without elaborating on the software that drives them. I feel like I'm having to defend a lot of statements I haven't actually made with this answer, but that's probably my fault for making it so brief. | |
| Nov 14, 2017 at 17:42 | comment | added | Tommy | @supercat on the VIA the CB1 input can act to clock the shifter, which samples CB2. An interrupt is generated upon a full byte. That's the process Commodore intended to use for serial receipt and transmission. But there's a bug in the VIA whereby it doesn't shift (or shifts twice, I forget) if the external clock is signalled within a certain close duration of the beginning of clock phase 2. So bit banging was the fallback. | |
| Nov 14, 2017 at 17:25 | comment | added | supercat | @Tommy: The VIA and CIA both had synchronous serial ports. I don't think either had the logic necessary to watch for a start bit and generate a bit clock that was delayed half a bit period from the falling edge. The VIA and CIA serial ports were intended to communicate with synchronous serial peripherals; I don't think they were ever intended for use as UARTs. | |
| Nov 14, 2017 at 17:07 | comment | added | Tommy | @supercat yes, but unintentionally. The VIA has that analogue race condition with clock phase and the shifter, and as I understand it, a CIA trace is missing on the C64 board. But, regardless, those are the chips which definitely are not UARTs which are electrically responsible for those serial ports. | |
| Nov 14, 2017 at 16:58 | comment | added | supercat | @Tommy: Both the VIC-20 and C64 used software-based bit-bang UARTs. | |
| Nov 14, 2017 at 4:14 | comment | added | Tommy | Right. The Vic-20 used a VIA, the C64 a CIA, it's safe to assume the Spectrum was built intentionally to bit bang, but the IBM PC had always used a chip called a UART, and the name of the PC's chip has attached itself to the port in many cases. Much like how tty is nearly synonymous with 'console', despite almost nobody having seen a teletype in years and a teletype not being required for a console. | |
| Nov 14, 2017 at 2:55 | comment | added | Jim MacKenzie | Serial ports needn't have UART chips (see: Commodore 64; Amiga 500). UARTs have small buffers that reduce the odds of characters getting dropped at higher speeds. So, you could say a UART is always part of a serial port, but a serial port doesn't always have a UART. | |
| Nov 14, 2017 at 2:17 | history | answered | Tommy | CC BY-SA 3.0 |