Xerox 560 Reference Manual page 77

2 3 4 Result of Shift
- a
No overflow on left shift.
- Overflow on left shift.
Searching shift terminated with
Ra
equal to 1.
At the completion of right shifts, the condition code is set
as follows:
2 3 4
a a
Logical Shift, Single Register
If the shift count, C, is positive, the contents of register R
are shifted left C places, the O's copied into vacated bit
positions on the right. (Bits shifted past RO are lost.) If C
is negative, the contents of register R are shifted right
Ici
places, with O's copied into vacated bit positions on the
left. (Bits shifted past R31 are lost.)
Affected: (R), CC1, CC2
Logical Shift, Double Register
o
1 2
n r
£.,J
If
the shift count, C, is positive, the contents of registers
Rand Ru1 are shifted left C places, with O's copied into
vacated bit positions on the right. Bits shifted past bit
position
a
of register Ru1 are copied into bit position 31
of register R. (Bits shifted past RO are lost.) If C is nega-
tive, the contents of registers Rand Ru1 are shifted right
Ici
places with O's copied into vacated bit positions on the
left. Bits shifted past bit position 31 of register Rare
copied into bit position
a
of register Ru 1. (Bits shifted
past Ru 131 are lost.)
Affected: (R), (Ru1), CC1, CC2
Circular Shift, Single Register
If the shift count, C, is positive, the contents of register R
are shifted left C places. Bits shifted 'past bit position 0
are copied into bit position 31. (No bits are lost.)
If
C
is negative, the contents of register R are shifted right
lei
places. Bits shifted past bit position 31 are copied
into bit position O. (No bits are lost.)
Affected: (R), CC1, CC2
Circular Shift, Double Register
If
the shift count, C, is positive, the contents of registers R
and Rul are shifted left C places. Bits shifted past bit
position
a
of register R are copied into bit position 31
of reg i ster Ru
1.
(No bi ts are lost.)
If
Cis negati ve, the
contents of registers Rand Rul are shifted right
lei
places.
Bits shifted past bit position 31 of register Ru1 are copied
into bit position 0 of register R. (No bits are lost.)
Affected: (R), (Rul), CC1, CC2
Arithmetic Shift, Single Register
If the shift count, C, is positive, the contents of register R
are shifted left C places, with O's copied into vacated bit
positions on the right. (Bits shifted past RO are lost.)
If
C
is negative, the contents of register R are shifted right
lei
places, with the contents of bit position
a
copied into va-
cated bit positions on the left. (Bits shifted past R31
are lost.)
Affected: (R), CC1, CC2
Arithmetic Shift, Double Register
If the shift count, C, is positive, the contents of register R
and Rul are shifted left C places, with O's copied into va-
cated bit positions on the right. Bits shifted past bit posi-
tion
a
of register Ru1 are copied into bit position 31 of
register R. (Bits shifted past RO are lost.) If C is negative,
the contents of registers Rand Ru1 are shifted right
Ici
places, with the contents of bit position
a
of register R
copied into vacated bit positions on the left. Bits shifted
past bit position 31 of register R are copied into bit posi-
tion
a
of register Ru1. (Bits shifted past Ru131 are lost.)
Affected: (R), (Rul), CC1, CC2
Searching Shift, Single Register
The searching shift is circular in either direction. If the
shift count, C, is positive, the contents of register Rare
shifted left C bit positions or unti
I
a 1 appears in bit posi-
tion O. If C is negative, the contents are shifted right
Ici
positions or unti
I
a 1 appears in bit position O. When the
shift is terminated, the remaining count is stored in regis-
ter 1, which is dedicated to the searching shift instruction.
Shift Instructions 71