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Cray CRAY-1 - Ba Register; La Register; Dead Start Sequence

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to
indicate
the
error
correction.
The
monitor
program
upon
resuming
execution determines the cause
of
the
interrupt
and
takes appropriate
action,
perhaps terminating the user program.
BA
REGISTER
The
18-bit
BA
register
holds the base address
of
the user
field
during
the execution
interval
for each exchange package.
The
contents of
this
register
are
interpreted
as the upper
18
bits
of
a
22-bit
memory
address.
The
lower four
bits
of the address are
assumed
zero. Absolute
memory
addresses are
formed
by
adding
(BA)
*
16
to the
relative
address specified
by
the
CPU
instructions.
The
BA
register
always indicates a
bank
0
memory
address.
LA
REGISTER
The
18-bit
LA
register
holds the
limit
address
of
the user
field
during
the execution interval for each exchange package.
The
contents of
LA
are
interpreted
as
the upper
18
bits
of
a
22-bit
memory
address.
The
lower four
bits
of
the address are
assumed
zero.
The
LA
register
always
indicates
a
bank
0
memory
address.
The
final address
that
can
be
executed
or
referenced
by
a
program
is
at
[(LA)
x 2
4
J -
1.
Note
that
the
(LA)
is
absolute, not
relative;
it
is
not
added
to
(BA).
DEAD
START
SEQUENCE
The
dead
start
sequence
is
that
sequence
of
operations required to
start
a
program
running in the
CPU
after
power
has
been
turned
off
and
then
turned
on
again.
All
registers
in the machine,
all
control
latches,
and
all
words
in
memory
are
assumed
to
be
invalid
after
power
has
been
turned on.
The
sequence
of
operations required to begin a
program
is
initiated
by
the maintenance control
unit.
This
unit
sequences the
following operations:
1. Turns
on
master
clear
signal.
2. Turns
on
I/O
clear
signal.
2240004
3-47 E

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