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SYSTEM
OBJECTS
STRUCTURES
Above
the
block
transfer
information,
a copy
of
the
information
contained
in
each
of
the
processor-resident
map
entr
ies
(0
through
4)
is
represented
by
a
data
structure
with
the
following
organization.
= =
double
byte
1----------------1
displacement
1
base
disp.
4
1----------------1
1 mask 1
1--------7-------1
base
address
1----------------1
1
entry
state
1 a
1----------------1
=
=
The
entry
state
field
is
used
to
describe
the
current
state
of
the
given
map
entry.
It
has
the
following
organization.
1 9
bits
lx1xx1xx1x1xl
1 1
1 1
1--
map
valid
1
1----
transfer
mode
!
1------
transfer
direction
1---------
transfer
state
1
1------------
memory
overlay
1------------------
reserved
The
I-bit
map
valid
subfield
indicates
whether
or
not
this
map
entry
is
currently
in
use.
If
the
bit
is
zero,
this
map
entry
is
not
used
in
Peripheral
Subsystem
address
inspection.
If
the
bit
is
one,
this
map
entry
is
used
in
Peripheral
Subsystem
address
inspection.
The
processor-resident
copy
of
this
subfield
is
checked
by
the
mapping
facility
each
time
a
Peripheral
Subsystem
address
is
received
for
inspection.
For
map
entry
0,
the
I-bit
transfer
mode
subfield
indicates
whether
this
map
entry
is
in
randan
or
block
transfer
mode. A
value
of
zero
indicates
that
this
map
entry
is
in
random mode. A
value
of
one
indicates
that
this
map
entry
is
in
block
transfer
mode.
For
map
entry
1,
the
I-bit
transfer
mode
subfield
indicates
whether
this
map
entry
maps
Peripheral
Subsystem
addresses
into
the
432
address
space
or
the
interconnection
address
space.
A
value
of
zero
indicates
that
this
map
entry
is
in
432 mapping mode. A
value
of
one
indicates
that
this
map
entry
is
in
interconnection
mapping mode.
For
other
map
entries,
the
setting
of
this
subfield
causes
a
fault.
A-17