<s>
VMEbus	B-Architecture
(	O
Versa	B-Architecture
Module	I-Architecture
Eurocard	I-Architecture
bus	O
)	O
is	O
a	O
computer	B-General_Concept
bus	I-General_Concept
standard	O
,	O
originally	O
developed	O
for	O
the	O
Motorola	B-Device
68000	I-Device
line	I-Device
of	O
CPUs	B-General_Concept
,	O
but	O
later	O
widely	O
used	O
for	O
many	O
applications	O
and	O
standardized	O
by	O
the	O
IEC	O
as	O
ANSI/IEEE	O
1014-1987	O
.	O
</s>
<s>
It	O
is	O
physically	O
based	O
on	O
Eurocard	O
sizes	O
,	O
mechanicals	O
and	O
connectors	O
(	O
DIN	B-Application
41612	O
)	O
,	O
but	O
uses	O
its	O
own	O
signalling	O
system	O
,	O
which	O
Eurocard	O
does	O
not	O
define	O
.	O
</s>
<s>
In	O
1979	O
,	O
during	O
development	O
of	O
the	O
Motorola	B-Device
68000	I-Device
CPU	B-General_Concept
,	O
one	O
of	O
their	O
engineers	O
,	O
Jack	B-Architecture
Kister	I-Architecture
,	O
decided	O
to	O
set	O
about	O
creating	O
a	O
standardized	O
bus	O
system	O
for	O
68000-based	O
systems	O
.	O
</s>
<s>
The	O
Motorola	O
team	O
brainstormed	O
for	O
days	O
to	O
select	O
the	O
name	O
VERSAbus	B-Architecture
.	O
</s>
<s>
VERSAbus	B-Architecture
cards	O
were	O
large	O
,	O
,	O
and	O
used	O
edge	O
connectors	O
.	O
</s>
<s>
Only	O
a	O
few	O
products	O
adopted	O
it	O
,	O
including	O
the	O
IBM	B-Device
System	I-Device
9000	I-Device
instrument	O
controller	O
and	O
the	O
Automatix	B-Application
robot	O
and	O
machine	O
vision	O
systems	O
.	O
</s>
<s>
A	O
young	O
engineer	O
working	O
for	O
Black	O
,	O
Julie	O
Keahey	O
designed	O
the	O
first	O
VERSAmodule	O
card	O
,	O
the	O
VERSAbus	B-Architecture
Adaptor	O
Module	O
,	O
used	O
to	O
run	O
existing	O
cards	O
on	O
the	O
new	O
VERSAbus	B-Architecture
.	O
</s>
<s>
The	O
result	O
was	O
first	O
known	O
as	O
VERSAbus-E	O
but	O
was	O
later	O
renamed	O
to	O
VMEbus	B-Architecture
,	O
for	O
VERSAmodule	O
Eurocard	O
bus	O
(	O
although	O
some	O
refer	O
to	O
it	O
as	O
Versa	O
Module	O
Europa	O
)	O
.	O
</s>
<s>
At	O
this	O
point	O
,	O
a	O
number	O
of	O
other	O
companies	O
involved	O
in	O
the	O
68000	B-Device
's	O
ecosystem	O
agreed	O
to	O
use	O
the	O
standard	O
,	O
including	O
Signetics	O
,	O
Philips	O
,	O
Thomson	O
,	O
and	O
Mostek	O
.	O
</s>
<s>
Soon	O
it	O
was	O
officially	O
standardized	O
by	O
the	O
IEC	O
as	O
the	O
IEC	O
821	O
VMEbus	B-Architecture
and	O
by	O
ANSI	O
and	O
IEEE	O
as	O
ANSI/IEEE	O
1014-1987	O
.	O
</s>
<s>
The	O
original	O
standard	O
was	O
a	O
16-bit	B-Device
bus	O
,	O
designed	O
to	O
fit	O
within	O
the	O
existing	O
Eurocard	O
DIN	B-Application
connectors	O
.	O
</s>
<s>
The	O
current	O
VME64	O
includes	O
a	O
full	O
64-bit	B-Device
bus	O
in	O
6U-sized	O
cards	O
and	O
32-bit	O
in	O
3U	O
cards	O
.	O
</s>
<s>
Other	O
associated	O
standards	O
have	O
added	O
hot-swapping	O
(	O
plug-and-play	B-Device
)	O
in	O
VME64x	O
,	O
smaller	O
'	O
IP	O
 '	O
cards	O
that	O
plug	O
into	O
a	O
single	O
VMEbus	B-Architecture
card	O
,	O
and	O
various	O
interconnect	B-General_Concept
standards	O
for	O
linking	O
VME	O
systems	O
together	O
.	O
</s>
<s>
The	O
VITA	O
Standards	O
Organization	O
called	O
for	O
a	O
new	O
standard	O
for	O
unmodified	O
VME32/64	O
backplanes	B-Architecture
.	O
</s>
<s>
Some	O
examples	O
are	O
IP	O
Module	O
,	O
RACEway	O
Interlink	O
,	O
SCSA	O
,	O
Gigabit	O
Ethernet	O
on	O
VME64x	O
Backplanes	B-Architecture
,	O
PCI	B-Protocol
Express	O
,	O
RapidIO	O
,	O
StarFabric	O
and	O
InfiniBand	O
.	O
</s>
<s>
VMEbus	B-Architecture
was	O
also	O
used	O
to	O
develop	O
closely	O
related	O
standards	O
,	O
VXIbus	B-Architecture
and	O
VPX	B-Architecture
.	O
</s>
<s>
The	O
VMEbus	B-Architecture
had	O
a	O
strong	O
influence	O
on	O
many	O
later	O
computer	B-General_Concept
buses	I-General_Concept
such	O
as	O
STEbus	B-Architecture
.	O
</s>
<s>
The	O
architectural	O
concepts	O
of	O
the	O
VMEbus	B-Architecture
are	O
based	O
on	O
VERSAbus	B-Architecture
,	O
developed	O
in	O
the	O
late	O
1970s	O
by	O
Motorola	O
.	O
</s>
<s>
Motorola	O
's	O
European	O
Microsystems	O
group	O
in	O
Munich	O
,	O
West	O
Germany	O
,	O
proposed	O
the	O
development	O
of	O
a	O
VERSAbus-like	O
product	O
line	O
based	O
on	O
the	O
Eurocard	O
mechanical	O
standard	O
.	O
</s>
<s>
To	O
demonstrate	O
the	O
concept	O
,	O
Max	O
Loesel	O
and	O
Sven	O
Rau	O
developed	O
three	O
prototype	O
boards	O
:	O
(	O
1	O
)	O
a	O
68000	B-Device
CPU	B-General_Concept
board	O
;	O
(	O
2	O
)	O
a	O
dynamic	O
memory	O
board	O
;	O
(	O
3	O
)	O
a	O
static	O
memory	O
board	O
.	O
</s>
<s>
They	O
named	O
the	O
new	O
bus	O
VERSAbus-E	O
.	O
</s>
<s>
These	O
companies	O
were	O
all	O
early	O
supporters	O
of	O
the	O
68000	B-Device
microprocessor	I-Device
family	O
.	O
</s>
<s>
John	O
Black	O
of	O
Motorola	O
,	O
Craig	O
MacKenna	O
of	O
Mostek	O
and	O
Cecil	O
Kaplinsky	O
of	O
Signetics	O
developed	O
the	O
first	O
draft	O
of	O
the	O
VMEbus	B-Architecture
specification	O
.	O
</s>
<s>
In	O
October	O
1981	O
,	O
at	O
the	O
System	O
'	O
81	O
trade	O
show	O
in	O
Munich	O
,	O
West	O
Germany	O
,	O
Motorola	O
,	O
Mostek	O
,	O
Signetics/Philips	O
,	O
and	O
Thomson	O
CSF	O
announced	O
their	O
joint	O
support	O
of	O
the	O
VMEbus	B-Architecture
.	O
</s>
<s>
In	O
August	O
1982	O
,	O
Revision	O
B	O
of	O
the	O
VMEbus	B-Architecture
specification	O
was	O
published	O
by	O
the	O
newly	O
formed	O
VMEbus	B-Architecture
Manufacturers	O
 '	O
Group	O
(	O
VITA	O
)	O
.	O
</s>
<s>
In	O
latter	O
1982	O
,	O
the	O
French	O
delegation	O
of	O
the	O
International	O
Electrotechnical	O
Commission	O
(	O
IEC	O
)	O
proposed	O
Revision	O
B	O
of	O
the	O
VMEbus	B-Architecture
as	O
an	O
international	O
standard	O
.	O
</s>
<s>
The	O
IEC	O
SC47B	O
subcommittee	O
nominated	O
Mira	O
Pauker	O
of	O
Philips	O
,	O
France	O
,	O
the	O
chairperson	O
of	O
an	O
editorial	O
committee	O
,	O
thus	O
formally	O
starting	O
international	O
standardization	O
of	O
the	O
VMEbus	B-Architecture
.	O
</s>
<s>
In	O
March	O
1983	O
,	O
the	O
IEEE	O
Microprocessor	O
Standards	O
Committee	O
(	O
MSC	O
)	O
requested	O
authorization	O
to	O
establish	O
a	O
working	O
group	O
that	O
could	O
standardize	O
the	O
VMEbus	B-Architecture
in	O
the	O
US	O
.	O
</s>
<s>
The	O
IEC	O
,	O
IEEE	O
and	O
VMEbus	B-Architecture
Manufacturers	O
Group	O
(	O
now	O
VITA	O
)	O
distributed	O
copies	O
of	O
Revision	O
B	O
for	O
comment	O
and	O
received	O
the	O
resulting	O
requests	O
for	O
changes	O
to	O
the	O
document	O
.	O
</s>
<s>
The	O
VMEbus	B-Architecture
Manufacturers	O
Group	O
labelled	O
the	O
document	O
Revision	O
C.1	O
and	O
placed	O
it	O
in	O
the	O
public	O
domain	O
.	O
</s>
<s>
In	O
1985	O
,	O
Aitech	O
developed	O
under	O
contract	O
for	O
US	O
TACOM	O
,	O
the	O
first	O
conduction-cooled	O
6U	O
VMEbus	B-Architecture
board	O
.	O
</s>
<s>
Although	O
electrically	O
providing	O
a	O
compliant	O
VMEbus	B-Architecture
protocol	O
interface	O
,	O
mechanically	O
,	O
this	O
board	O
was	O
not	O
interchangeable	O
for	O
use	O
in	O
air-cooled	O
lab	O
VMEbus	B-Architecture
development	O
chassis	O
.	O
</s>
<s>
In	O
late	O
1987	O
,	O
a	O
technical	O
committee	O
was	O
formed	O
under	O
VITA	O
under	O
the	O
direction	O
of	O
IEEE	O
to	O
create	O
the	O
first	O
military	O
,	O
conduction-cooled	O
6U×	O
160mm	O
,	O
fully	O
electrically	O
and	O
mechanically	O
compatible	O
,	O
VMEbus	B-Architecture
board	O
co-chaired	O
by	O
Dale	O
Young	O
(	O
DY4	O
Systems	O
)	O
and	O
Doug	O
Patterson	O
(	O
Plessey	O
Microsystems	O
,	O
then	O
Radstone	O
Technology	O
)	O
.	O
</s>
<s>
ANSI/IEEE	O
-1101.2-1992	O
was	O
later	O
ratified	O
and	O
released	O
in	O
1992	O
and	O
remains	O
in	O
place	O
as	O
the	O
conduction-cooled	O
,	O
international	O
standard	O
for	O
all	O
6U	O
VMEbus	B-Architecture
products	O
.	O
</s>
<s>
In	O
1989	O
,	O
John	O
Peters	O
of	O
Performance	O
Technologies	O
Inc	O
.	O
developed	O
the	O
initial	O
concept	O
of	O
VME64	O
:	O
multiplexing	O
address	O
and	O
data	O
lines	O
(	O
A64/D64	O
)	O
on	O
the	O
VMEbus	B-Architecture
.	O
</s>
<s>
The	O
concept	O
was	O
demonstrated	O
the	O
same	O
year	O
and	O
placed	O
in	O
the	O
VITA	O
Technical	O
Committee	O
in	O
1990	O
as	O
a	O
performance	O
enhancement	O
to	O
the	O
VMEbus	B-Architecture
specification	O
.	O
</s>
<s>
In	O
1991	O
,	O
the	O
PAR	O
(	O
Project	O
Authorization	O
Request	O
)	O
for	O
P1014R	O
(	O
revisions	O
to	O
the	O
VMEbus	B-Architecture
specification	O
)	O
was	O
granted	O
by	O
the	O
IEEE	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
1992	O
,	O
the	O
additional	O
enhancements	O
to	O
VMEbus	B-Architecture
(	O
A40/D32	O
,	O
Locked	O
Cycles	O
,	O
Rescinding	O
DTACK*	O
,	O
Autoslot-ID	O
,	O
Auto	O
System	O
Controller	O
,	O
and	O
enhanced	O
DIN	B-Application
connector	O
mechanicals	O
)	O
required	O
more	O
work	O
to	O
complete	O
this	O
document	O
.	O
</s>
<s>
The	O
VITA	O
Technical	O
Committee	O
returned	O
to	O
using	O
the	O
public	O
domain	O
VMEbus	B-Architecture
C.1	O
specification	O
as	O
their	O
base-level	O
document	O
,	O
to	O
which	O
they	O
added	O
new	O
enhancements	O
.	O
</s>
<s>
Two	O
other	O
activities	O
began	O
in	O
late	O
1992	O
:	O
BLLI	O
(	O
VMEbus	B-Architecture
Board-level	O
Live	O
Insertion	O
Specifications	O
)	O
and	O
VSLI	O
(	O
VMEbus	B-Architecture
System-level	O
Live	O
Insertion	O
with	O
Fault	O
Tolerance	O
)	O
.	O
</s>
<s>
In	O
many	O
ways	O
the	O
VMEbus	B-Architecture
is	O
equivalent	O
or	O
analogous	O
to	O
the	O
pins	O
of	O
the	O
68000	B-Device
run	O
out	O
onto	O
a	O
backplane	B-Architecture
.	O
</s>
<s>
However	O
,	O
one	O
of	O
the	O
key	O
features	O
of	O
the	O
68000	B-Device
is	O
a	O
flat	O
32-bit	O
memory	O
model	O
,	O
free	O
of	O
memory	B-General_Concept
segmentation	I-General_Concept
and	O
other	O
"	O
anti-features	O
"	O
.	O
</s>
<s>
The	O
result	O
is	O
that	O
,	O
while	O
VME	O
is	O
very	O
68000-like	O
,	O
the	O
68000	B-Device
is	O
generic	O
enough	O
to	O
make	O
this	O
not	O
an	O
issue	O
in	O
most	O
cases	O
.	O
</s>
<s>
Like	O
the	O
68000	B-Device
,	O
VME	O
uses	O
separate	O
32-bit	O
data	O
and	O
address	O
buses	O
.	O
</s>
<s>
The	O
68000	B-Device
address	O
bus	O
is	O
actually	O
24-bit	O
and	O
the	O
data	B-General_Concept
bus	I-General_Concept
16-bit	B-Device
(	O
although	O
it	O
is	O
32/32	O
internally	O
)	O
but	O
the	O
designers	O
were	O
already	O
looking	O
towards	O
a	O
full	O
32-bit	O
implementation	O
.	O
</s>
<s>
Reading	O
data	O
is	O
essentially	O
the	O
same	O
but	O
the	O
controlling	O
card	O
drives	O
the	O
address	O
bus	O
,	O
leaves	O
the	O
data	B-General_Concept
bus	I-General_Concept
tri-stated	O
and	O
drives	O
the	O
read	O
pin	O
.	O
</s>
<s>
The	O
slave	O
card	O
drives	O
read	O
data	O
onto	O
the	O
data	B-General_Concept
bus	I-General_Concept
and	O
drives	O
the	O
data	O
strobe	O
pins	O
low	O
when	O
the	O
data	O
is	O
ready	O
.	O
</s>
<s>
The	O
signalling	O
scheme	O
is	O
asynchronous	O
,	O
meaning	O
that	O
the	O
transfer	O
is	O
not	O
tied	O
to	O
the	O
timing	O
of	O
a	O
bus	O
clock	O
pin	O
(	O
unlike	O
synchronous	O
buses	O
such	O
as	O
PCI	B-Protocol
)	O
.	O
</s>
<s>
Address	O
modifiers	O
are	O
used	O
to	O
divide	O
the	O
VME	B-Architecture
bus	I-Architecture
address	O
space	O
into	O
several	O
distinct	O
sub-spaces	O
.	O
</s>
<s>
The	O
address	O
modifier	O
is	O
a	O
6	O
bit	O
wide	O
set	O
of	O
signals	O
on	O
the	O
backplane	B-Architecture
.	O
</s>
<s>
VME	O
also	O
decodes	O
all	O
seven	O
of	O
the	O
68000	B-Device
's	O
interrupt	B-Application
levels	O
onto	O
a	O
7-pin	O
interrupt	B-Application
bus	O
.	O
</s>
<s>
The	O
interrupt	B-Application
scheme	O
is	O
one	O
of	O
prioritized	O
vectored	O
interrupts	B-Application
.	O
</s>
<s>
The	O
interrupt	B-Application
request	O
lines	O
(	O
IRQ1	O
–	O
IRQ7	O
)	O
prioritize	O
interrupts	B-Application
.	O
</s>
<s>
An	O
interrupting	B-Application
module	O
asserts	O
one	O
of	O
the	O
interrupt	B-Application
request	O
lines	O
.	O
</s>
<s>
any	O
interrupt	B-Application
.	O
</s>
<s>
When	O
an	O
interrupt	B-Application
handling	I-Application
module	O
recognizes	O
an	O
interrupt	B-Application
request	O
at	O
a	O
priority	O
it	O
handles	O
,	O
it	O
arbitrates	O
for	O
the	O
bus	O
in	O
the	O
usual	O
fashion	O
described	O
above	O
.	O
</s>
<s>
It	O
then	O
performs	O
a	O
read	O
of	O
the	O
interrupt	B-Application
vector	O
by	O
driving	O
the	O
binary	O
version	O
of	O
the	O
IRQ	O
line	O
it	O
handles	O
(	O
e.g.	O
</s>
<s>
The	O
interrupter	O
responds	O
by	O
transferring	O
a	O
status/ID	O
on	O
the	O
data	B-General_Concept
bus	I-General_Concept
to	O
describe	O
the	O
interrupt	B-Application
.	O
</s>
<s>
The	O
interrupt	B-Application
handling	I-Application
module	O
(	O
usually	O
a	O
CPU	B-General_Concept
)	O
will	O
usually	O
use	O
this	O
status/ID	O
number	O
to	O
identify	O
and	O
run	O
the	O
appropriate	O
software	O
interrupt	B-Application
service	O
routine	O
.	O
</s>
<s>
On	O
the	O
VME	B-Architecture
bus	I-Architecture
,	O
all	O
transfers	O
are	O
DMA	B-General_Concept
and	O
every	O
card	O
is	O
a	O
master	O
or	O
slave	O
.	O
</s>
<s>
For	O
instance	O
,	O
with	O
the	O
ISA	B-Architecture
bus	I-Architecture
,	O
both	O
of	O
these	O
features	O
had	O
to	O
be	O
added	O
alongside	O
the	O
existing	O
"	O
channels	O
"	O
model	O
,	O
whereby	O
all	O
communications	O
was	O
handled	O
by	O
the	O
host	O
CPU	B-General_Concept
.	O
</s>
<s>
When	O
developing	O
and/or	O
troubleshooting	O
the	O
VME	B-Architecture
bus	I-Architecture
,	O
examination	O
of	O
hardware	O
signals	O
can	O
be	O
very	O
important	O
.	O
</s>
<s>
Computers	O
using	O
VMEbus	B-Architecture
include	O
:	O
</s>
<s>
Seen	O
looking	O
into	O
backplane	B-Architecture
socket	O
.	O
</s>
<s>
P2	O
rows	O
a	O
and	O
c	O
can	O
be	O
used	O
by	O
a	O
secondary	O
bus	O
,	O
for	O
example	O
the	O
STEbus	B-Architecture
.	O
</s>
