EIA RS-232 serial line interface - Revision history

Jnc: New cat

2022-05-23T12:53:40Z

New cat

← Older revision		Revision as of 12:53, 23 May 2022
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	===Grounds===		===Grounds===

	~~From [https://en.wikipedia.org/wiki/~~RS-232 ~~Wikipedia]~~:		{{Wikipedia\|RS-232}}:

	Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous [[ground loop]]. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422 and RS-485 can tolerate larger ground voltage differences because of the differential signaling.		Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous [[ground loop]]. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422 and RS-485 can tolerate larger ground voltage differences because of the differential signaling.
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	* [[EIA RS-422 serial line interface]]		* [[EIA RS-422 serial line interface]]

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

Jnc: Also used on sync lines

2020-10-19T11:54:59Z

Also used on sync lines

← Older revision		Revision as of 11:54, 19 October 2020
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	The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[~~asynchronous~~ serial line]] interface using which was commonly used to connect both terminals and modems to computers.		The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[serial line]] interface using which was commonly used to connect both terminals and modems to computers.

	RS-232 uses [[single-ended signalling‎]] at the electrical level, with an [[Non Return to Zero\|NRZ]] encoding system; the closely related descendant [[EIA RS-422 serial line interface]] uses [[differential pair]]s instead. The other, older, option for such communications is [[20mA current loop serial line interface\|20mA current loop]]).		RS-232 uses [[single-ended signalling‎]] at the electrical level, with an [[Non Return to Zero\|NRZ]] encoding system; the closely related descendant [[EIA RS-422 serial line interface]] uses [[differential pair]]s instead. The other, older, option for such communications is [[20mA current loop serial line interface\|20mA current loop]]).
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	\|}		\|}

	The Request To Send (sometimes 'Ready to Send') and Clear To Send pair are for [[hardware]] [[flow control]], but use of them is fairly rare.		The Request To Send (sometimes 'Ready To Send') and Clear To Send pair are for [[hardware]] [[flow control]], but use of them is fairly rare.

	The signal [[ground]] provides a [[voltage]] reference for all the other signals, and also serves as a common [[signal return]] for them.		The signal [[ground]] provides a [[voltage]] reference for all the other signals, and also serves as a common [[signal return]] for them.
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	Confusingly, these are the opposite from the original [[asynchronous serial line]], in which idle was a high voltage (so that a break in the line, or the failure of the transmitter, was easily detectable.) Data bits are also inverted, logically - 1 is a negative voltage, and 0 is positive.		Confusingly, these are the opposite from the original [[asynchronous serial line]], in which idle was a high voltage (so that a break in the line, or the failure of the transmitter, was easily detectable.) Data bits are also inverted, logically - 1 is a negative voltage, and 0 is positive.

	Signal voltages in the range between −3V to +3V are thus not valid RS-232 levels; the maximum slew rate is also limited. To maximize robustness, RS-232 interfaces have be able to withstand being indefinitely shorted to ground. or tied to any voltage up to 25 volts (positive or negative).		Signal voltages in the range between −3V to +3V are thus not valid RS-232 levels; the maximum slew rate is also limited. To maximize robustness, RS-232 interfaces have be able to withstand being indefinitely shorted to ground, or tied to any voltage up to 25 volts (positive or negative).

	===Grounds===		===Grounds===
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	From [https://en.wikipedia.org/wiki/RS-232 Wikipedia]:		From [https://en.wikipedia.org/wiki/RS-232 Wikipedia]:

	Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485~~, and USB~~ can tolerate larger ground voltage differences because of the differential signaling.		Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous [[ground loop]]. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422 and RS-485 can tolerate larger ground voltage differences because of the differential signaling.

	==See also==		==See also==

Jnc: uses NRZ encoding

2020-05-10T10:15:52Z

uses NRZ encoding

← Older revision		Revision as of 10:15, 10 May 2020
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	The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[asynchronous serial line]] interface using which was commonly used to connect both terminals and modems to computers.		The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[asynchronous serial line]] interface using which was commonly used to connect both terminals and modems to computers.

	RS-232 uses [[single-ended signalling‎]] at the electrical level; the closely related descendant [[EIA RS-422 serial line interface]] uses [[differential pair]]s instead. The other, older, option for such communications is [[20mA current loop serial line interface\|20mA current loop]]).		RS-232 uses [[single-ended signalling‎]] at the electrical level, with an [[Non Return to Zero\|NRZ]] encoding system; the closely related descendant [[EIA RS-422 serial line interface]] uses [[differential pair]]s instead. The other, older, option for such communications is [[20mA current loop serial line interface\|20mA current loop]]).

	RS-232 comes in two 'sexes', the 'Data Communication Equipment' ('''DCE'''), usually properly found on modems, and the 'Data Terminal Equipment' ('''DTE'''), usually properly found on terminals and computers. The concept was that at each end of the link, a DTE would plug into a DCE; the two modems with the DCEs would communicate over a telephone line.		RS-232 comes in two 'sexes', the 'Data Communication Equipment' ('''DCE'''), usually properly found on modems, and the 'Data Terminal Equipment' ('''DTE'''), usually properly found on terminals and computers. The concept was that at each end of the link, a DTE would plug into a DCE; the two modems with the DCEs would communicate over a telephone line.

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2019-07-26T22:38:59Z

Grounds: +See also

← Older revision		Revision as of 22:38, 26 July 2019
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	Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.		Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.

			==See also==

			* [[EIA RS-422 serial line interface]]

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

Jnc: better cat

2018-12-13T19:01:24Z

better cat

← Older revision		Revision as of 19:01, 13 December 2018
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	Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.		Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.

	[[Category: ~~Device Basics‎‎~~]]		[[Category: Communication Basics]]

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2018-12-13T15:14:52Z

+cat

← Older revision		Revision as of 15:14, 13 December 2018
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	Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.		Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.

			[[Category: Device Basics‎‎]]

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2018-09-30T20:04:33Z

RTS/CTS flow control

← Older revision		Revision as of 20:04, 30 September 2018
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	\|}		\|}

	The signal [[ground]] provides a [[voltage]] reference for all the other signals, and also serves as a common return for them.		The Request To Send (sometimes 'Ready to Send') and Clear To Send pair are for [[hardware]] [[flow control]], but use of them is fairly rare.

			The signal [[ground]] provides a [[voltage]] reference for all the other signals, and also serves as a common [[signal return]] for them.

	===Null modem wiring===		===Null modem wiring===

Jnc: +link

2018-09-30T18:54:57Z

+link

← Older revision		Revision as of 18:54, 30 September 2018
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	===Grounds===		===Grounds===

	From Wikipedia:		From [https://en.wikipedia.org/wiki/RS-232 Wikipedia]:

	Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.		Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end, and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential serial connections such as RS-422, RS-485, and USB can tolerate larger ground voltage differences because of the differential signaling.

Jnc: Add RS422

2018-05-22T00:09:47Z

Add RS422

← Older revision		Revision as of 00:09, 22 May 2018
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	The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[asynchronous serial line]] interface which was commonly used to connect both terminals and modems to computers ~~(the other option for such communications being [[20mA current loop serial line interface\|20mA current loop]])~~.		The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[asynchronous serial line]] interface using which was commonly used to connect both terminals and modems to computers.

	It comes in two 'sexes', the 'Data Communication Equipment' ('''DCE'''), usually properly found on modems, and the 'Data Terminal Equipment' ('''DTE'''), usually properly found on terminals and computers. The concept was that at each end of the link, a DTE would plug into a DCE; the two modems with the DCEs would communicate over a telephone line.		RS-232 uses [[single-ended signalling‎]] at the electrical level; the closely related descendant [[EIA RS-422 serial line interface]] uses [[differential pair]]s instead. The other, older, option for such communications is [[20mA current loop serial line interface\|20mA current loop]]).

			RS-232 comes in two 'sexes', the 'Data Communication Equipment' ('''DCE'''), usually properly found on modems, and the 'Data Terminal Equipment' ('''DTE'''), usually properly found on terminals and computers. The concept was that at each end of the link, a DTE would plug into a DCE; the two modems with the DCEs would communicate over a telephone line.

	Connecting a terminal to a computer (both wired as DTEs) thus usually requires a so-called '''null modem''', a small device wired on both sides as a DCE. Internally, it connects appropriate signals together, so that e.g. one side's 'Transmitted Data' signal is connected to the other side's 'Received Data'. (In theory, there could be a DCE-DCE connecting device, but in practice this combination never occurs.)		Connecting a terminal to a computer (both wired as DTEs) thus usually requires a so-called '''null modem''', a small device wired on both sides as a DCE. Internally, it connects appropriate signals together, so that e.g. one side's 'Transmitted Data' signal is connected to the other side's 'Received Data'. (In theory, there could be a DCE-DCE connecting device, but in practice this combination never occurs.)
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	\|}		\|}

	The signal ground provides a voltage reference for all the other signals, and also serves as a common return for them.		The signal [[ground]] provides a [[voltage]] reference for all the other signals, and also serves as a common return for them.

	===Null modem wiring===		===Null modem wiring===
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	==Electrical==		==Electrical==

	The asynchronous serial line protocol requires two signal levels: idle (mark), and asserted (space). In RS-232, the former is indicated by a voltage level in the range of -3V to -15V (with respect to the "Signal Ground" pin; the latter by a voltage level in the range of +3V to +15V.		The asynchronous serial line protocol requires two signal levels: idle (mark), and asserted (space). In the single-sided RS-232, the former is indicated by a voltage level in the range of -3V to -15V (with respect to the "Signal Ground" pin; the latter by a voltage level in the range of +3V to +15V.

	Confusingly, these are the opposite from the original [[asynchronous serial line]], in which idle was a high voltage (so that a break in the line, or the failure of the transmitter, was easily detectable.) Data bits are also inverted, logically - 1 is a negative voltage, and 0 is positive.		Confusingly, these are the opposite from the original [[asynchronous serial line]], in which idle was a high voltage (so that a break in the line, or the failure of the transmitter, was easily detectable.) Data bits are also inverted, logically - 1 is a negative voltage, and 0 is positive.

Jnc: avoid redir

2017-01-13T22:25:41Z

avoid redir

← Older revision		Revision as of 22:25, 13 January 2017
Line 1:		Line 1:
	The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[asynchronous serial line]] interface which was commonly used to connect both terminals and modems to computers (the other option for such communications being [[20mA current loop]]).		The '''EIA RS-232 serial line interface''' standard (now often known simply as '''RS-232''', or '''EIA''') is an [[asynchronous serial line]] interface which was commonly used to connect both terminals and modems to computers (the other option for such communications being [[20mA current loop serial line interface\|20mA current loop]]).

	It comes in two 'sexes', the 'Data Communication Equipment' ('''DCE'''), usually properly found on modems, and the 'Data Terminal Equipment' ('''DTE'''), usually properly found on terminals and computers. The concept was that at each end of the link, a DTE would plug into a DCE; the two modems with the DCEs would communicate over a telephone line.		It comes in two 'sexes', the 'Data Communication Equipment' ('''DCE'''), usually properly found on modems, and the 'Data Terminal Equipment' ('''DTE'''), usually properly found on terminals and computers. The concept was that at each end of the link, a DTE would plug into a DCE; the two modems with the DCEs would communicate over a telephone line.