1822 interface - Revision history

Jnc: Explain 'ready/test' pairs now that we have the diagram; consistent tense

2025-01-15T12:39:22Z

Explain 'ready/test' pairs now that we have the diagram; consistent tense

← Older revision		Revision as of 12:39, 15 January 2025
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	[[Image:BBN-1822-IMP-host-interface.jpg\|thumb\|right\|400px\|IMP-host interface signals]]		[[Image:BBN-1822-IMP-host-interface.jpg\|thumb\|right\|400px\|IMP-host interface signals; note the relays on the two 'ready/test' pairs]]

	The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.		The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.
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	It was originally specified for use in connecting a [[host]] to an [[Interface Message Processor\|IMP]] on the [[ARPANET]], leading to the common naming of [[device controller]]s which produced an 1822 interface as [[IMP interface]]s; a number of different host 1822 interfaces were produced over the years. Somewhat later, the 1822 interface was adopted for the interface used to connect to the PRUs of the early [[Packet Radio Network‎‎]]; this was likely due in part because of the easy availability of a large range of host interfaces.		It was originally specified for use in connecting a [[host]] to an [[Interface Message Processor\|IMP]] on the [[ARPANET]], leading to the common naming of [[device controller]]s which produced an 1822 interface as [[IMP interface]]s; a number of different host 1822 interfaces were produced over the years. Somewhat later, the 1822 interface was adopted for the interface used to connect to the PRUs of the early [[Packet Radio Network‎‎]]; this was likely due in part because of the easy availability of a large range of host interfaces.

	At the very lowest layer, there ~~are~~ two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs ~~use~~ to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)		At the very lowest layer, there were two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there was also a third, the 'Very Distant Host' (VDH), but it was an entirely different system from the other two; it was a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs used to talk to each other, allowing a host to be many miles from the IMP it was attached to. It was not at all similar to the interface discussed here, so is not covered here.)

	The first two ~~are~~ operationally the same, and differ only in the lowest-level physical details: LH ~~uses~~ [[~~Single~~-ended signalling\|single-sided]] [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH ~~uses~~ [[differential pair]]s, with ground isolation on the IMP end.		The first two were operationally the same, and differ only in the lowest-level physical [[analog]] details: LH used [[single-ended signalling\|single-sided]] [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH used [[differential pair]]s, with ground isolation on the IMP end.

	The 1822 interface also included two pairs of 'ready' lines (one pair from the IMP, and one from the Host); one conductor of each pair was connected to the other ~~(which was usually connected to ground)~~ via a [[relay]] when that ~~entity~~ wanted to signal that it is ~~ready~~.		The 1822 interface also included two pairs of 'ready/test' lines (one pair from the IMP, and one from the Host); one conductor of each pair was connected to the other via a [[relay]] at the responsible machine's end when that machine wanted to signal that it was ready. (One of the pair was usually connected to ground at the source; the other line could then be tested to see is it too was at ground.)

	There was no fixed [[word]] length, the IMP was prepared to talk to machines with different word lengths.		There was no fixed [[word]] length, the IMP was prepared to talk to machines with different word lengths.

Larsbrinkhoff: Picture of signals.

2025-01-15T12:11:59Z

Picture of signals.

← Older revision		Revision as of 12:11, 15 January 2025
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	[[Image:BBN-1822-IMP-host-interface.jpg\|thumb\|right\|400px\|IMP-host interface signals]]		[[Image:BBN-1822-IMP-host-interface.jpg\|thumb\|right\|400px\|IMP-host interface signals]]


	The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.		The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.

Larsbrinkhoff: Picture of interface signals.

2025-01-15T12:09:31Z

Picture of interface signals.

← Older revision		Revision as of 12:09, 15 January 2025
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			[[Image:BBN-1822-IMP-host-interface.jpg\|thumb\|right\|400px\|IMP-host interface signals]]


	The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.		The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.

Jnc: LH was single-sided

2022-06-28T19:49:43Z

LH was single-sided

← Older revision		Revision as of 19:49, 28 June 2022
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	At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)		At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)

	The first two are operationally the same, and differ only in the lowest-level physical details: LH uses [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH uses [[differential pair]]s, with ground isolation on the IMP end.		The first two are operationally the same, and differ only in the lowest-level physical details: LH uses [[Single-ended signalling\|single-sided]] [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH uses [[differential pair]]s, with ground isolation on the IMP end.

	The 1822 interface also included two pairs of 'ready' lines (one pair from the IMP, and one from the Host); one conductor of each pair was connected to the other (which was usually connected to ground) via a [[relay]] when that entity wanted to signal that it is ready.		The 1822 interface also included two pairs of 'ready' lines (one pair from the IMP, and one from the Host); one conductor of each pair was connected to the other (which was usually connected to ground) via a [[relay]] when that entity wanted to signal that it is ready.

Jnc: Clean up to follow 1822/IMP interface split

2021-11-08T16:53:07Z

Clean up to follow 1822/IMP interface split

← Older revision		Revision as of 16:53, 8 November 2021
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	The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) is [[bit-serial]] data transfer interface used in [[data network]]ing~~; it~~ was originally specified for use in connecting a [[host]] to an [[Interface Message Processor\|IMP]] on the [[ARPANET]]~~. It is~~ [[~~asynchronous~~]]~~, with a handshake on every bit; there is no fixed~~ [[~~word~~]] ~~length~~, the ~~IMP~~ was ~~prepared~~ to ~~talk~~ to ~~machines with different word lengths~~.		The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) was [[bit-serial]] data transfer interface used in [[data network]]ing. It was [[asynchronous]], with a handshake on every bit.

			It was originally specified for use in connecting a [[host]] to an [[Interface Message Processor\|IMP]] on the [[ARPANET]], leading to the common naming of [[device controller]]s which produced an 1822 interface as [[IMP interface]]s; a number of different host 1822 interfaces were produced over the years. Somewhat later, the 1822 interface was adopted for the interface used to connect to the PRUs of the early [[Packet Radio Network‎‎]]; this was likely due in part because of the easy availability of a large range of host interfaces.

	At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)		At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)
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	The first two are operationally the same, and differ only in the lowest-level physical details: LH uses [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH uses [[differential pair]]s, with ground isolation on the IMP end.		The first two are operationally the same, and differ only in the lowest-level physical details: LH uses [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH uses [[differential pair]]s, with ground isolation on the IMP end.

	The 1822 interface also ~~includes~~ two pairs of 'ready' lines (one pair from the IMP, and one from the Host); one conductor of each pair is connected to the other (which is usually connected to ground) via a [[relay]] when that entity ~~wants~~ to signal that it is ready.		The 1822 interface also included two pairs of 'ready' lines (one pair from the IMP, and one from the Host); one conductor of each pair was connected to the other (which was usually connected to ground) via a [[relay]] when that entity wanted to signal that it is ready.

	A number of different [[IMP interface\|1822 host interfaces]] were produced over the years. Somewhat later, the 1822 interface was adopted for the interface used to connect to the PRUs of the early [[Packet Radio Network‎‎]]; this was likely due in part because of the easy availability of a large range of host interfaces.

	~~==Host interfaces==~~

	~~These were some of the most popular:~~

	* [[IMP11-A ARPANET interface]]
	* [[LH-DH/11 Local/Distant Host Controller]]
	* [[MLH-DH/LSI11 Multiple Channel Controller]]
	* [[Stanford 1822 Interface]]

	~~but there were many others (many being 'one-off' local creations)~~.		There was no fixed [[word]] length, the IMP was prepared to talk to machines with different word lengths.

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

Jnc: more specific category

2021-11-08T15:23:44Z

more specific category

← Older revision		Revision as of 15:23, 8 November 2021
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	The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) is [[bit-serial]] data transfer interface used in [[data network]]ing; it was originally specified for use in connecting a [[host]] to an [[IMP]] on the [[ARPANET]]. It is [[asynchronous]], with a handshake on every bit; there is no fixed [[word]] length, the IMP was prepared to talk to machines with different word lengths.		The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) is [[bit-serial]] data transfer interface used in [[data network]]ing; it was originally specified for use in connecting a [[host]] to an [[Interface Message Processor\|IMP]] on the [[ARPANET]]. It is [[asynchronous]], with a handshake on every bit; there is no fixed [[word]] length, the IMP was prepared to talk to machines with different word lengths.

	At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)		At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)
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	* BBN Report #1822, [http://www.bitsavers.org/pdf/bbn/imp/BBN1822_Jan1976.pdf Specification for the Interconnection of a Host and an IMP] - The 1976 revision of this key document		* BBN Report #1822, [http://www.bitsavers.org/pdf/bbn/imp/BBN1822_Jan1976.pdf Specification for the Interconnection of a Host and an IMP] - The 1976 revision of this key document

	[[Category: ~~Network~~ Interfaces]]		[[Category: 1822 Interfaces]]
	~~[[Category: ARPANET~~]]

Jnc: +cat

2021-11-06T00:23:52Z

+cat

← Older revision		Revision as of 00:23, 6 November 2021
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	[[Category: Network Interfaces]]		[[Category: Network Interfaces]]
			[[Category: ARPANET]]

Jnc: Split off for use by PR article

2021-11-02T17:18:47Z

Split off for use by PR article

← Older revision		Revision as of 17:18, 2 November 2021
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	~~#Redirect~~ [[Host-to-IMP ~~Protocol~~]]		The '''1822 interface''' (named after the number of the [[Bolt, Beranek, and Newman\|BBN]] report which specified it) is [[bit-serial]] data transfer interface used in [[data network]]ing; it was originally specified for use in connecting a [[host]] to an [[IMP]] on the [[ARPANET]]. It is [[asynchronous]], with a handshake on every bit; there is no fixed [[word]] length, the IMP was prepared to talk to machines with different word lengths.

			At the very lowest layer, there are two different choices for the [[physical layer]]; 'Local Host' (LH), and 'Distant Host' (DH). (Technically, there is also a third, the 'Very Distant Host' (VDH), but it is an entirely different system from the other two; it is a [[synchronous serial line]] through a [[modem]], exactly the same as the system which the IMPs use to talk to each other, allowing a host to be many miles from the IMP it is attached to. It is not at all similar to the interface discussed here, so is not covered here.)

			The first two are operationally the same, and differ only in the lowest-level physical details: LH uses [[transistor-transistor logic\|TTL]] signals over [[twisted pair]]s, with a [[ground]] being the other [[conductor]] in the pair; DH uses [[differential pair]]s, with ground isolation on the IMP end.

			The 1822 interface also includes two pairs of 'ready' lines (one pair from the IMP, and one from the Host); one conductor of each pair is connected to the other (which is usually connected to ground) via a [[relay]] when that entity wants to signal that it is ready.

			A number of different [[IMP interface\|1822 host interfaces]] were produced over the years. Somewhat later, the 1822 interface was adopted for the interface used to connect to the PRUs of the early [[Packet Radio Network‎‎]]; this was likely due in part because of the easy availability of a large range of host interfaces.

			==Host interfaces==

			These were some of the most popular:

			* [[IMP11-A ARPANET interface]]
			* [[LH-DH/11 Local/Distant Host Controller]]
			* [[MLH-DH/LSI11 Multiple Channel Controller]]
			* [[Stanford 1822 Interface]]

			but there were many others (many being 'one-off' local creations).

			==See also==

			* BBN Report #1822, [http://www.bitsavers.org/pdf/bbn/imp/BBN1822_Jan1976.pdf Specification for the Interconnection of a Host and an IMP] - The 1976 revision of this key document

			[[Category: Network Interfaces]]

Jnc: Redir - Covered there

2021-10-30T18:03:23Z

Redir - Covered there

New page

#Redirect [[Host-to-IMP Protocol]]