Asynchronous serial line - Revision history

Jnc: /* See also */ +QBUS asynchronous serial interfaces

2024-07-25T13:06:53Z

See also: +QBUS asynchronous serial interfaces

← Older revision		Revision as of 13:06, 25 July 2024
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	* [[Synchronous serial line]]		* [[Synchronous serial line]]
			* [[QBUS asynchronous serial interfaces]]

	==External links==		==External links==

Jnc: /* See also */ +Synchronous serial line

2023-07-18T21:05:18Z

Jnc: New cat

2022-05-23T12:57:22Z

New cat

← Older revision		Revision as of 12:57, 23 May 2022
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	* [https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss23.1 Linux Serial how-to (extensive)]		* [https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss23.1 Linux Serial how-to (extensive)]

	[[Category: ~~Communication Basics~~]]		[[Category: Serial Lines]]

Jnc: /* Common settings */ fix grammar

2022-05-23T11:01:46Z

Common settings: fix grammar

← Older revision		Revision as of 11:01, 23 May 2022
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	==Common settings==		==Common settings==

	~~Common settings with~~ 8 data bits, no parity bit, and 1 stop bit; with the required start bit, ~~which~~ leads to a ~~bit-grouping~~ of exactly 10 bits, which makes throughput calculations simple (bits-per-second/10 = ~~[[character]]s~~ per second).		A common setting uses 8 data bits, no parity bit, and 1 stop bit; with the required start bit, this leads to a [[character]] size, in the transmission, of exactly 10 bits, which makes throughput calculations simple (bits-per-second/10 = characters per second).

	~~Common settings~~ for remote terminals was to force all ~~caps~~, ~~and~~ only ~~needing~~ 5 bits per character (which did not, however have enough code points to allow for numerals, as well as a complete alphabet - 2^5=32). It was thought that it would speed throughput, but at such low data rates, the savings were not significant.		A common setting for remote terminals was to force all capital letters, which only needed 5 bits per character (which did not, however have enough code points to allow for numerals, as well as the complete alphabet - 2^5=32). It was thought that it would speed throughput, but at such low data rates, the savings were not significant.

	==UART==		==UART==

Jnc: /* UART */ do separate page

2021-11-18T11:30:27Z

UART: do separate page

← Older revision		Revision as of 11:30, 18 November 2021
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	==UART==		==UART==

	The complete ~~circuitry~~ needed to originate and interpret serial line signals, including the serial-parallel conversion, was implemented in one of the first [[MSI]] chips, the Universal Asynchronous Receiver/Transmitter (UART). The circuitry needed to produce the ~~voltages~~ and ~~currents~~ needed by the particular interface type was outside the chip, so a UART could be used with either EIA or 20mA interfaces.		The complete [[circuit]]ry needed to originate and interpret serial line signals, including the serial-[[parallel]] conversion, was implemented in one of the first [[MSI]] [[integrated circuit\|chips]], the [[Universal Asynchronous Receiver/Transmitter]] (UART). The circuitry needed to produce the [[voltage]]s and [[current]]s needed by the particular interface type was outside the chip, so a UART could be used with either [[EIA RS-232 serial line interface\|EIA]] or [[20mA current loop serial line interface\|20mA]] interfaces.

	~~===UART Buffers===~~
	With increased speeds, besides locking the DCE-DTE rate at 2x the communication rate, UART chips would need to increase their local buffer size to be able to send continuously. It did not help that a UART chip was released with a defective buffer, or that in some cases, the buffers would need to be enabled.

	==References==		==References==

Jnc: +phys layer

2021-08-05T14:49:56Z

+phys layer

← Older revision		Revision as of 14:49, 5 August 2021
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	'''Asynchronous serial lines''' were the most common interface to computers for many decades; originally they connected printing [[terminal]]s like the [[Teletype]], and later [[video terminal]]s such as the [[VT100]]. In general, asynchronous [[serial line]] interfaces were bi-directional, using separate wires for each direction (although there are counter-examples, such as printers).		'''Asynchronous serial lines''' were the most common interface to computers for many decades; originally they connected printing [[terminal]]s like the [[Teletype]], and later [[video terminal]]s such as the [[VT100]]. In general, asynchronous [[serial line]] interfaces were bi-directional, using separate wires for each direction (although there are counter-examples, such as printers).

	There were two different common electrical interface specifications, [[20mA current loop serial line interface]], and later [[EIA RS-232 serial line interface]], but they both used the same logical interface protocol at a higher layer. EIA supported operation through [[modem]]s, but ~~20ma~~ was ~~strictly~~ for local devices.		There were two different common electrical interface specifications, [[20mA current loop serial line interface]], and later [[EIA RS-232 serial line interface]], but they both used the same logical interface protocol at a higher layer, and differed only at the [[physical layer]] ([[voltage]], [[current]], etc). EIA supported operation through [[modem]]s, but 20mA was mostly used for local devices.

	There is no separate [[clock]] or other control signal; rather, the data stream itself has [[synchronization]] information, which marks the start and end of each character.		There is no separate [[clock]] or other control signal; rather, the data stream itself has [[synchronization]] information, which marks the start and end of each character.
Line 7:		Line 7:
	[[Image:AsynSerialLine.jpg\|right\|Transmission format]]		[[Image:AsynSerialLine.jpg\|right\|Transmission format]]

	Characters are sent as sequence (see image, right) of up to four fields: a 1-bit ''start'' marker; 5-8 data bits; an optional parity bit; and a ''stop'' marker of 1, 1.5 or 2 bits. The speed, data size, and parity must be externally configured into the transmitter and receiver; the stop width is set in the former.		Characters are sent as sequence (see image, right) of up to four fields: a 1-[[bit]] ''start'' marker; 5-8 data bits; an optional [[parity]] bit; and a ''stop'' marker of 1, 1.5 or 2 bits. The speed, data size, and parity must be externally configured into the transmitter and receiver; the stop width is set in the former.

	The line starts at idle; when a character is ready to be sent, one 'start' bit of space (confusingly, on an EIA interface, high voltage) marks the start of a character. The data is then sent, one bit at a time, least-significant-bit first. Finally, the appropriate number of 'stop' bits are sent as mark (low on an EIA interface). If no other characters are ready to be sent, the line is then left at idle (~~mark~~), otherwise the sending of the next character starts immediately, with another start bit.		The line starts at idle; when a character is ready to be sent, one 'start' bit of space (confusingly, on an EIA interface, high voltage) marks the start of a character. The data is then sent, one bit at a time, least-significant-bit first. Finally, the appropriate number of 'stop' bits are sent as mark (low voltage on an EIA interface). If no other characters are ready to be sent, the line is then left at idle (space), otherwise the sending of the next character starts immediately, with another start bit.

	==Break==		==Break==
Line 15:		Line 15:
	If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and sent specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.		If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and sent specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.

	== Common settings ==		==Common settings==

	Common settings with 8 data bits, no parity bit, and 1 stop bit, with the required start bit, which leads to a bit-~~packet~~ of exactly 10 bits, which makes throughput calculations simple. ( bits-per-second/10 = ~~Characters~~ per second ).		Common settings with 8 data bits, no parity bit, and 1 stop bit; with the required start bit, which leads to a bit-grouping of exactly 10 bits, which makes throughput calculations simple (bits-per-second/10 = [[character]]s per second).

	Common settings for remote terminals was to force all caps, and only needing 5 bits per character (which did not have enough code points to allow for numerals, as well as a complete alphabet). It was thought that it would speed throughput, but at such low data rates, the savings were not significant.		Common settings for remote terminals was to force all caps, and only needing 5 bits per character (which did not, however have enough code points to allow for numerals, as well as a complete alphabet - 2^5=32). It was thought that it would speed throughput, but at such low data rates, the savings were not significant.

	==UART==		==UART==
Line 25:		Line 25:
	The complete circuitry needed to originate and interpret serial line signals, including the serial-parallel conversion, was implemented in one of the first [[MSI]] chips, the Universal Asynchronous Receiver/Transmitter (UART). The circuitry needed to produce the voltages and currents needed by the particular interface type was outside the chip, so a UART could be used with either EIA or 20mA interfaces.		The complete circuitry needed to originate and interpret serial line signals, including the serial-parallel conversion, was implemented in one of the first [[MSI]] chips, the Universal Asynchronous Receiver/Transmitter (UART). The circuitry needed to produce the voltages and currents needed by the particular interface type was outside the chip, so a UART could be used with either EIA or 20mA interfaces.

	==UART Buffers==		===UART Buffers===
	With increased speeds, besides locking the DCE-DTE rate at 2x the communication rate, UART chips would need to increase their local buffer size to be able to send continuously. It did not help that a UART chip was released with a defective buffer, or that in some cases, the buffers would need to be enabled.		With increased speeds, besides locking the DCE-DTE rate at 2x the communication rate, UART chips would need to increase their local buffer size to be able to send continuously. It did not help that a UART chip was released with a defective buffer, or that in some cases, the buffers would need to be enabled.

	==References==		==References==
	[https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss23.1 Linux Serial how-to (extensive)]
			* [https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss23.1 Linux Serial how-to (extensive)]

	[[Category: Communication Basics]]		[[Category: Communication Basics]]

Jnc: RS-232 specific info shoud be in RS-232 page - much of this is already there

2020-07-02T13:26:34Z

RS-232 specific info shoud be in RS-232 page - much of this is already there

← Older revision		Revision as of 13:26, 2 July 2020
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	If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and sent specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.		If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and sent specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.

	== ~~RS-232 Standard and common~~ settings ==		== Common settings ==
	The RS-232 standard defines the two devices connected with a serial cable as the Data Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE). This terminology reflects the RS-232 origin as a standard for communication between a computer terminal and a modem.

	Common settings with 8 data bits, no parity bit, and 1 stop bit, with the required start bit, which leads to a bit-packet of exactly 10 bits, which makes throughput calculations simple. ( bits-per-second/10 = Characters per second ).		Common settings with 8 data bits, no parity bit, and 1 stop bit, with the required start bit, which leads to a bit-packet of exactly 10 bits, which makes throughput calculations simple. ( bits-per-second/10 = Characters per second ).

	Common settings for remote terminals was to force all caps, and only needing 5 bits per character, It was thought that it would speed throughput, but at such low data rates, the savings were not significant.		Common settings for remote terminals was to force all caps, and only needing 5 bits per character (which did not have enough code points to allow for numerals, as well as a complete alphabet). It was thought that it would speed throughput, but at such low data rates, the savings were not significant.

	~~Speed would commonly be set at the fastest rate that did not have errors:~~
	~~Common for ttys: was 45, 90 and 120 baud.~~
	~~Common for VTD was 1200, 2400 and 4800,~~
	~~Later as communication chips improved, 9600, 14400 and 19200.~~

	~~Most common speeds were Baud rate: 9600 or 115200.~~

	~~Between DTE and DCE modems, you could lock the carrier rates, and increase the RS-232 rate at 2x the carrier rates, eliminating any bottle neck in the local circuitry.~~

	==UART==		==UART==
Line 40:		Line 30:
	==References==		==References==
	[https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss23.1 Linux Serial how-to (extensive)]		[https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss23.1 Linux Serial how-to (extensive)]



	[[Category: Communication Basics]]		[[Category: Communication Basics]]

ForOldHack: /* DCE and refrences */ Need common word size for VT-52 terminals.

2020-06-22T21:06:40Z

DCE and refrences: Need common word size for VT-52 terminals.

@@ Line 13: / Line 13: @@
 ==Break==
-If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and signalled specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.
+If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and sent specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.
 ==UART==
 The complete circuitry needed to originate and interpret serial line signals, including the serial-parallel conversion, was implemented in one of the first [[MSI]] chips, the Universal Asynchronous Receiver/Transmitter (UART). The circuitry needed to produce the voltages and currents needed by the particular interface type was outside the chip, so a UART could be used with either EIA or 20mA interfaces.
 [[Category: Communication Basics]]

Jnc: reorder to define before use

2020-03-21T16:05:22Z

reorder to define before use

← Older revision		Revision as of 16:05, 21 March 2020
Line 1:		Line 1:
	'''Asynchronous serial lines''' were the most common interface to computers for many decades; originally they connected printing [[terminal]]s like the [[Teletype]], and later [[video terminal]]s such as the [[VT100]]. In general, asynchronous [[serial line]] interfaces were bi-directional, using separate wires for each direction (although there are counter-examples, such as printers).		'''Asynchronous serial lines''' were the most common interface to computers for many decades; originally they connected printing [[terminal]]s like the [[Teletype]], and later [[video terminal]]s such as the [[VT100]]. In general, asynchronous [[serial line]] interfaces were bi-directional, using separate wires for each direction (although there are counter-examples, such as printers).

	There is no separate clock or other control signal; rather, the data stream itself has [[synchronization]] information, which marks the start and end of each character.		There were two different common electrical interface specifications, [[20mA current loop serial line interface]], and later [[EIA RS-232 serial line interface]], but they both used the same logical interface protocol at a higher layer. EIA supported operation through [[modem]]s, but 20ma was strictly for local devices.

			There is no separate [[clock]] or other control signal; rather, the data stream itself has [[synchronization]] information, which marks the start and end of each character.

	[[Image:AsynSerialLine.jpg\|right\|Transmission format]]		[[Image:AsynSerialLine.jpg\|right\|Transmission format]]
Line 8:		Line 10:

	The line starts at idle; when a character is ready to be sent, one 'start' bit of space (confusingly, on an EIA interface, high voltage) marks the start of a character. The data is then sent, one bit at a time, least-significant-bit first. Finally, the appropriate number of 'stop' bits are sent as mark (low on an EIA interface). If no other characters are ready to be sent, the line is then left at idle (mark), otherwise the sending of the next character starts immediately, with another start bit.		The line starts at idle; when a character is ready to be sent, one 'start' bit of space (confusingly, on an EIA interface, high voltage) marks the start of a character. The data is then sent, one bit at a time, least-significant-bit first. Finally, the appropriate number of 'stop' bits are sent as mark (low on an EIA interface). If no other characters are ready to be sent, the line is then left at idle (mark), otherwise the sending of the next character starts immediately, with another start bit.

	There were two different common electrical interface specifications, [[20mA current loop serial line interface]], and later [[EIA RS-232 serial line interface]], but they both used the same logical interface protocol at a higher layer. EIA supported operation through [[modem]]s, but 20ma was strictly for local devices.

	==Break==		==Break==

	If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and signalled specially. This is often used to interrupt the computer on the other end of the line from the terminal.		If the line is held in the 'space' state for longer than a character time, this is called a '''break''' condition, and it can be detected by the receiver and signalled specially. This is often used to [[interrupt]] the computer on the other end of the line from the terminal.

	==UART==		==UART==

Jnc: move mark/space to ser line

2020-03-21T14:09:48Z

move mark/space to ser line

← Older revision		Revision as of 14:09, 21 March 2020
Line 1:		Line 1:
	'''Asynchronous serial lines''' were the most common interface to computers for many decades; originally they connected printing [[terminal]]s like the [[Teletype]], and later [[video terminal]]s such as the [[VT100]]. In general, asynchronous [[serial line]] interfaces were bi-directional, using separate wires for each direction (although there are counter-examples, such as printers).		'''Asynchronous serial lines''' were the most common interface to computers for many decades; originally they connected printing [[terminal]]s like the [[Teletype]], and later [[video terminal]]s such as the [[VT100]]. In general, asynchronous [[serial line]] interfaces were bi-directional, using separate wires for each direction (although there are counter-examples, such as printers).

	There is no separate clock or other control signal; rather, the data stream itself has [[synchronization]] information, which marks the start and end of each character. The asynchronous serial line protocol requires two signal levels: idle (mark, high), and asserted (space, low). (The polarity is a legacy from telegraphy, where the line was held high in order to show that the line was not broken, and that the transmitter was functional.)		There is no separate clock or other control signal; rather, the data stream itself has [[synchronization]] information, which marks the start and end of each character.

	[[Image:AsynSerialLine.jpg\|right\|Transmission format]]		[[Image:AsynSerialLine.jpg\|right\|Transmission format]]

← Older revision		Revision as of 21:05, 18 July 2023
Line 25:		Line 25:
	The complete [[circuit]]ry needed to originate and interpret serial line signals, including the serial-[[parallel]] conversion, was implemented in one of the first [[MSI]] [[integrated circuit\|chips]], the [[Universal Asynchronous Receiver/Transmitter]] (UART). The circuitry needed to produce the [[voltage]]s and [[current]]s needed by the particular interface type was outside the chip, so a UART could be used with either [[EIA RS-232 serial line interface\|EIA]] or [[20mA current loop serial line interface\|20mA]] interfaces.		The complete [[circuit]]ry needed to originate and interpret serial line signals, including the serial-[[parallel]] conversion, was implemented in one of the first [[MSI]] [[integrated circuit\|chips]], the [[Universal Asynchronous Receiver/Transmitter]] (UART). The circuitry needed to produce the [[voltage]]s and [[current]]s needed by the particular interface type was outside the chip, so a UART could be used with either [[EIA RS-232 serial line interface\|EIA]] or [[20mA current loop serial line interface\|20mA]] interfaces.

	==~~References~~==		==See also==

	* [https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#~~ss23~~.1 Linux Serial ~~how-to (extensive)~~]		* [[Synchronous serial line]]

			==External links==

			* [https://www.tldp.org/HOWTO/html_single/Serial-HOWTO/#ss20.1 Linux Serial HOWTO]

	[[Category: Serial Lines]]		[[Category: Serial Lines]]