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

Larsbrinkhoff: Picture of signals.

2025-01-15T12:11:59Z

Picture of signals.

Larsbrinkhoff: Picture of interface signals.

2025-01-15T12:09:31Z

Picture of interface signals.

Jnc: LH was single-sided

2022-06-28T19:49:43Z

LH was single-sided

Jnc: Clean up to follow 1822/IMP interface split

2021-11-08T16:53:07Z

Clean up to follow 1822/IMP interface split

Jnc: more specific category

2021-11-08T15:23:44Z

more specific category

Jnc: +cat

2021-11-06T00:23:52Z

+cat

Jnc: Split off for use by PR article

2021-11-02T17:18:47Z

Split off for use by PR article

Jnc: Redir - Covered there

2021-10-30T18:03:23Z

Redir - Covered there

New page

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

@@ Line 1: / Line 1: @@
-[[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.
@@ Line 5: / Line 5: @@
 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.

← Older revision		Revision as of 12:11, 15 January 2025
Line 1:		Line 1:
	[[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.

← Older revision		Revision as of 12:09, 15 January 2025
Line 1:		Line 1:
		+	[[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.

@@ Line 5: / Line 5: @@
 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.

@@ Line 1: / Line 1: @@
-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.
 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.)
@@ Line 5: / Line 7: @@
 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.
-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==

@@ Line 1: / Line 1: @@
-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.)
@@ Line 24: / Line 24: @@
 * 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]]

← Older revision		Revision as of 00:23, 6 November 2021
Line 25:		Line 25:

	[[Category: Network Interfaces]]		[[Category: Network Interfaces]]
		+	[[Category: ARPANET]]

← Older revision		Revision as of 17:18, 2 November 2021
Line 1:		Line 1:
−	~~#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]]