Alto Hardware Manual
Section 3: Emulator
22
conventions).
DREAD
610lSB Double-word read (Alto II only):
ACO+-
rv(AC3);
ACI
+-
rv(Ac3
XOR
1)
DWRITE
61016B
Double-word write
(Alto)!
only):
rv(AC3)+-
ACO;
rv(Ac3
XOR
I)+-
Acl
DEXCH 610l7B
Double-word exchange (Alto II only):
t+-
rv(AC3);
rv(AC3)+-
ACO;
ACO+-t
t+-
rv(Ac3
XOR
1); rv(Ac3
XOR
I)+-
Acl;
Acl
+-
t
DIAGNOSEl
61022B
Diagnostic instruction (Alto
II
only):
This instruction starts a special double-word write cycle that also writes the
Hamming
code check
bits.
rv(177026B)+-
Ac2 (set Hamming code)
rv(Ac3)+-
ACO;
rv(Ac3
XOR
I)+-
Acl
DIAGNOSE2
61023B
Diagnostic instruction (Alto II only):
BITBLT
This instruction writes the same memory location with two different values
in
quick succession:
rv(AC3)+-
ACO
rv(AC3)+-
ACO
xor
Acl
ACO+-
ACO
xor
ACI
61024B
Bit-boundary block transfer:
An instruction for moving bits
around
in memory. It is particularly helpful
for
dealing with
the
display
bit
map.
BITBLT
requires the
RAM
to
be
present in
order
to
use
some
S registers
(41B
through
SIB).
If
the
RAM
is
not
present, BITBLTwill trap as
if
it
were an unimplemented
operation.
CALLING
SEQUENCE
The
BITBLT
function
is
invoked with:
ACl:
0
AC2:
pointer to
BBTable,
which.
must
be
even.
Only Ac2
is
preserved by
BITBLT.
The most common errors when using this instruction are failing
to
align the
BBTable
on
an
even
word boundary, failing to zero
Acl,
and failing to zero
FUNCI10N[O-9].
The format
of
the
BBTable
is:
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