M782 Interrupt Control - Revision history

Jnc: /* External links */ +Coverage in early handbook

2023-11-28T02:04:17Z

‎External links: +Coverage in early handbook

Jnc: +Cat

2023-07-19T12:22:11Z

+Cat

Jnc: /* Images */ Another B-revision M7821

2022-04-11T13:01:06Z

‎Images: Another B-revision M7821

Jnc: /* Vectors */ jumper sense on M7821

2022-02-25T20:02:57Z

‎Vectors: jumper sense on M7821

Jnc: avoid redirs

2020-03-02T03:06:22Z

avoid redirs

Jnc: /* Revisions */ Add link to new page

2020-02-12T14:13:09Z

‎Revisions: Add link to new page

Jnc: /* Revisions */ copyedit

2020-02-07T16:55:56Z

‎Revisions: copyedit

Jnc: clarify etch revs

2020-02-07T13:57:08Z

clarify etch revs

Jnc: /* See also */ +ext links to flip chip site

2020-02-06T15:55:34Z

‎See also: +ext links to flip chip site

Jnc: +see also

2019-09-30T14:07:15Z

+see also

@@ Line 49: / Line 49: @@
 ==External links==
 * [http://so-much-stuff.com/pdp8/flipchip/modules.htm FlipChip Modules] - Images and engineering drawings for FLIP CHIP modules
 ** [http://svn.so-much-stuff.com/svn/trunk/Eagle/projects/DEC/Mxxx/M782/ M782]

← Older revision		Revision as of 12:22, 19 July 2023
Line 56:		Line 56:
	[[Category: UNIBUS]]		[[Category: UNIBUS]]
	[[Category: DEC Boards]]		[[Category: DEC Boards]]
		+	[[Category: DEC Documentation Errors]]

← Older revision		Revision as of 13:01, 11 April 2022
Line 38:		Line 38:

	The A interrupt block can allow a device to do multiple DMA cycles with a single bus grant, when pin J2 is left high; [[ground]]ing pin J2 signals that the DMA cycles are finished.		The A interrupt block can allow a device to do multiple DMA cycles with a single bus grant, when pin J2 is left high; [[ground]]ing pin J2 signals that the DMA cycles are finished.
		+
		+	==Images==
		+
		+	* [[:File:M7821.jpg\|Another B-revision M7821]]

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

@@ Line 27: / Line 27: @@
 ('''''Note:''''' The 1972 Edition of the 'Digital Logic Handbook' shows a jumper on address bit 2; however neither the prints, nor actual boards, agree with this.)
-The M7821 adds a jumper on address bit 2 (04); that bit can be controlled by either the device's electronics, or the jumper. (The sense of the vector jumpers is also inverted between the M7821 and the two previous versions.)
+The M7821 adds a jumper on address bit 2 (04); that bit can be controlled by either the device's electronics, or the jumper. (The sense of the vector jumpers is also inverted between the M7821 and the two previous versions; they are 'in' for '1', and 'out' for '0', on the M7821.)
 ===Operation===

@@ Line 3: / Line 3: @@
 The '''M782 Interrupt Control''' (later versions '''M7820''' and '''M7821''') is a [[Digital Equipment Corporation|DEC]] [[FLIP CHIP]] which implements the '[[interrupt]] control' function for the [[UNIBUS]]. It contains two separate interrupt [[circuit]] blocks; they can be wired to produce separate interrupts, or either can be used to provide the device with [[Direct Memory Access|DMA]] capability.
-It was used, usually along with an [[M105 Address Selector]], in early [[PDP-11]] [[device controller]]s which plugged into an [[Small Peripheral Controller|SPC]] slot. It was also used in a number of early devices which were built out of a custom [[backplane]] and a large number of FLIP CHIPs, such as the [[RK11|RK11-C]]. Some later devices which no longer used a large number of small Flip Chips (such as the [[TM11|TMB11]]) also used it.
+It was used, usually along with an [[M105 Address Selector]], in early [[PDP-11]] [[device controller]]s which plugged into an [[Small Peripheral Controller|SPC]] slot. It was also used in a number of early devices which were built out of a custom [[backplane]] and a large number of FLIP CHIPs, such as the [[RK11-C disk controller|RK11-C]]. Some later devices which no longer used a large number of small Flip Chips (such as the [[TM11 magtape controller|TMB11]]) also used it.
 ==Revisions==

@@ Line 11: / Line 11: @@
 This board, unlike the M105, appeared in a plethora of different versions; not just the M782 (above), M7820 (right) and M7821 (below), but also different [[printed circuit board|etch]] revisions of each, many of which differ very significantly from each other. (The number appears to have been changed for functionality/configuration changes; below).
-Although some of the changes are due to functionality changes, it appears that many of them were attempts to get rid of [[Meta-stability#Latches and arbiters|race]] issues in the [[bus grant|grant]]-passing circuity, which is often quite different between the versions. The import of the changes is not always completely clear, but the D version of the M7821, the last, contains a number of [[delay line]]s not present on the earlier models; this is significant because when the [[meta-stability]] issue at the heart of race problems was finally fully understood, it became clear that delays were the only 'solution'.
+Although some of the changes are due to functionality changes, it appears that many of them were attempts to get rid of [[race]] issues in the [[bus grant|grant]]-passing [[arbiter|arbitration]] circuity, which is often quite different between the versions. The import of the changes is not always completely clear, but the D version of the M7821, the last, contains a number of [[delay line]]s not present on the earlier models; this is significant because when the [[meta-stability]] issue at the heart of race problems was finally fully understood, it became clear that delays were the only 'solution'.
 The M782 seems to have appeared in revisions A though E (it is not known if there was an un-lettered initial version, but that does not seem to have been DEC practise at the time), although examples of the C and D are not extant (it is not known if they actually went into production). The M7820 appears to have had A-C, with only the C extant. The M7821 appears in A-D revisions, with the A not extant: the early one, marked 'M7821B' (below); the C (image [[:Image:M7821RevC.jpg|here]]), which is rare; and the D (bottom).

@@ Line 9: / Line 9: @@
 [[Image:M7820InterruptControl.jpg|250px|thumb|right|M7820, C revision etch]]
-This board, unlike the M105, appeared in a plethora of different versions; not just the M782 (above), M7820 (right) and M7821, but also different [[printed circuit board|etch]] revisions of each, many of which differ very significantly from each other. (The number appears to have been changed for functionality/configuration changes; below).
+This board, unlike the M105, appeared in a plethora of different versions; not just the M782 (above), M7820 (right) and M7821 (below), but also different [[printed circuit board|etch]] revisions of each, many of which differ very significantly from each other. (The number appears to have been changed for functionality/configuration changes; below).
-Although some of the changes are due to functionality changes, it appears that most of them were attempts to get rid of [[Meta-stability#Latches and arbiters|race]] issues in the [[bus grant|grant]]-passing circuity, which is usually quite different between the versions. The import of the changes is not completely clear, but the D version of the M7821, the last, contains a number of [[delay line]]s not present on the earlier models; this is significant because when the [[meta-stability]] issue at heart of race problems was finally fully understood, it became clear that delays were the only 'solution'.
+Although some of the changes are due to functionality changes, it appears that many of them were attempts to get rid of [[Meta-stability#Latches and arbiters|race]] issues in the [[bus grant|grant]]-passing circuity, which is often quite different between the versions. The import of the changes is not always completely clear, but the D version of the M7821, the last, contains a number of [[delay line]]s not present on the earlier models; this is significant because when the [[meta-stability]] issue at the heart of race problems was finally fully understood, it became clear that delays were the only 'solution'.
 The M782 seems to have appeared in revisions A though E (it is not known if there was an un-lettered initial version, but that does not seem to have been DEC practise at the time), although examples of the C and D are not extant (it is not known if they actually went into production). The M7820 appears to have had A-C, with only the C extant. The M7821 appears in A-D revisions, with the A not extant: the early one, marked 'M7821B' (below); the C (image [[:Image:M7821RevC.jpg|here]]), which is rare; and the D (bottom).

@@ Line 1: / Line 1: @@
-[[Image:M782InterruptControl.jpg|250px|thumb|right|M782]]
+[[Image:M782InterruptControl.jpg|250px|thumb|right|M782, A revision etch]]
 The '''M782 Interrupt Control''' (later versions '''M7820''' and '''M7821''') is a [[Digital Equipment Corporation|DEC]] [[FLIP CHIP]] which implements the '[[interrupt]] control' function for the [[UNIBUS]]. It contains two separate interrupt [[circuit]] blocks; they can be wired to produce separate interrupts, or either can be used to provide the device with [[Direct Memory Access|DMA]] capability.
@@ Line 7: / Line 7: @@
 ==Revisions==
-[[Image:M7820InterruptControl.jpg|250px|thumb|right|M7820]]
+[[Image:M7820InterruptControl.jpg|250px|thumb|right|M7820, C revision etch]]
-The [[bus grant|grant]]-passing circuity is quite different between the M7820 (right) and M7821; it is possible that it was changed to reduce a [[meta-stability|race]] issue, but the import of the changes is not clear.
+This board, unlike the M105, appeared in a plethora of different versions; not just the M782 (above), M7820 (right) and M7821, but also different [[printed circuit board|etch]] revisions of each, many of which differ very significantly from each other. (The number appears to have been changed for functionality/configuration changes; below).
-The M7821 appears in three [[printed circuit board|etch]] revisions: the early one, marked 'M7821B' (below); the C (image [[:Image:M7821RevC.jpg|here]]), which is rare; and the D (bottom). It is not known what the difference is, but again, it may relate to race issues between interrupt requests and grants; the D contains many more components than the C, including a number of [[delay line]]s not present on the earlier models.)
+Although some of the changes are due to functionality changes, it appears that most of them were attempts to get rid of [[Meta-stability#Latches and arbiters|race]] issues in the [[bus grant|grant]]-passing circuity, which is usually quite different between the versions. The import of the changes is not completely clear, but the D version of the M7821, the last, contains a number of [[delay line]]s not present on the earlier models; this is significant because when the [[meta-stability]] issue at heart of race problems was finally fully understood, it became clear that delays were the only 'solution'.
 ==Jumpers==
@@ Line 39: / Line 41: @@
 ==See also==
-* [[Bus Arbitration on the Unibus and QBUS]]
+* [[Bus Arbitration on the Unibus and QBUS]] - Goes into detail on the grant-passing race issue, and why a delay is the only 'solution'
 ==External links==

@@ Line 41: / Line 41: @@
 * [[Bus Arbitration on the Unibus and QBUS]]
-{{semi-stub}}
+==External links==
 [[Category: UNIBUS]]
 [[Category: DEC Boards]]

← Older revision		Revision as of 14:07, 30 September 2019
Line 36:		Line 36:

	The A interrupt block can allow a device to do multiple DMA cycles with a single bus grant, when pin J2 is left high; [[ground]]ing pin J2 signals that the DMA cycles are finished.		The A interrupt block can allow a device to do multiple DMA cycles with a single bus grant, when pin J2 is left high; [[ground]]ing pin J2 signals that the DMA cycles are finished.
		+
		+	==See also==
		+
		+	* [[Bus Arbitration on the Unibus and QBUS]]

	{{semi-stub}}		{{semi-stub}}