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HOST ACCESS TIMING
Copyright 1995, S
YS
I
RAN
Corp.
D-5
VME3U H/W REFERENCE
DTACK*
AS*
DSx*
HREQ
HACK
1
2
1.
AS to DSx
=
10 ns
(per VME Spec.)
2.
DSx to DTACK
=
186 ns
(Host Adapter time)
3.
DTACK to End of Cycle
=
0 ns
(per VME Spec.)
196 ns
NOTE: There is no Host Request (HREQ) because this is not an ASIC resource
Figure D-5 READ From External CSR
D.5 Access Times
Host access to shared memory is affected by two things:
•
Priority on contention between the two ports
•
Asynchronous request handling
There are minimum and maximum times which depend on Network WRITE priority and
the asynchronous handling of the requests. The minimum DPRC access times (i.e., no
contention between ports) are shown in. This table does not include host timing. The
“worst case” scenerio resulting in maximum access times would be a host WRITE
followed immediately by another host WRITE, and simultaneous receipt of three
network WRITES.
Minimum access times occur when there is no contention. Maximum access times result
when the worst possible case of contention occurs.
The SCRAMNet
+
cycle is initiated by the assertion of the Data Strobe (DS) and the de-
assertion of the Data Strobe (DS) as the end of the cycle.
D.5.1 Typical Access Sequence
The following is the typical Host READ and Host WRITE sequence with no contention.
READ
•
Address Strobe (AS) and Data Strobe fall (Start of cycle)
•
Host Request (HREQ) asserted
•
Host Request Pending (HREQ_PEND) asserted (DPRC accepts request)
•
DPRC READ shared memory and pass the data to Host-Interface Logic
•
De-assert HREQ_PEND
•
Host Acknowledge (HACK)
Содержание SCRAMNet+ VME3U
Страница 1: ...SCRAMNet Network VME3U Hardware Reference Document No D T MR VME3U A 0 A2...
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Страница 52: ...OPERATION Copyright 1995 SYSIRAN Corp 4 26 VME3U H W REFERENCE Figure 4 10 Quad Switch...
Страница 72: ...CSR DESCRIPTIONS Copyright 1995 SYSIRAN Corp 5 18 VME3U H W REFERENCE This page intentionally left blank...
Страница 73: ...Copyright 1995 SYSIRAN Corp 6 1 VME3U H W REFERENCE 6 0 PHYSICAL FEATURES Figure 6 12 VME3U Layout...
Страница 76: ...PHYSICAL FEATURES Copyright 1995 SYSIRAN Corp 6 4 VME3U H W REFERENCE This page intentionally left blank...
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Страница 100: ...SPECIFICATIONS Copyright 1995 SYSIRAN Corp C 4 VME3U H W REFERENCE C 5 Fiber Optic Bypass Switch...
Страница 101: ...SPECIFICATIONS Copyright 1995 SYSIRAN Corp C 5 VME3U H W REFERENCE Figure C 2 Fiber Optic Bypass Switch...
Страница 102: ...SPECIFICATIONS Copyright 1995 SYSIRAN Corp C 6 VME3U H W REFERENCE Figure C 3 Housing Dimensions...
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Страница 115: ...E APPENDIX E CONFIGURATION AIDS TABLE OF CONTENTS...
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Страница 120: ...CONFIGURATION AID Copyright 1995 SYSIRAN Corp E 4 VME3U H W REFERENCE This page intentionally left blank...
Страница 121: ...F APPENDIX F ACRONYMS...
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Страница 124: ...ACRONYM Copyright 1995 SYSlRAN Corp F 2 VME3U H W REFERENCE This page intentionally left blank...
Страница 125: ...G APPENDIX G GLOSSARY...
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Страница 134: ...GLOSSARY Copyright 1995 SYSlRAN Corp G 8 VME3U H W REFERENCE This page intentionally left blank...