Xerox 550 User Manual

original contents of register R, register Rul, CC1, CC3,
and CC4 unchanged; otherwise, the BP executes the next
instruction in sequence.
AWM ADD WORD TO MEMORyt
0/Vord index alignment)
ADD WORD TO MEMORY adds the contents of register R
to
the effective word and stores the sum in the effective
word location. The sum is stored regardless of whether or
not overflow occurs.
Affected: (EWL), CC
Trap: Fixed-pointoverflow
EW + (R)-EWL
Condition code settings:
2 3 4 Result in EWL
- 0 0 Zero
o Negative
o Positive
- 0
No fixed-point overflow
Fixed-point overflow
o No carry from bit position 0
- Carry from bit position 0
If CC2 is set to 1 and fixed-point arithmetic trap mask
(AM) is a 1,
the BP traps to location X'43' after the re-
sult is stored in the effective word location; otherwise, the
BP executes the next instruction in sequence.
MTB MODIFY AND TEST BYTE
t
(Byte
index alignment)
If the value of the R field is nonzero, the high-order bit of
the R field (bit position 8 of the instruction word) is ex-
tended 4 bit positions to the left, to form a byte with bit
positions 0-4 of that byte equal to the high-order bit of
t
This
instruction requires two memory references to the same
location for its execution. To preclude other processors
from
accessing the effective location during this time, the
memory unit containing the effective location is reserved
(not
accessible to other processors) unti I the instruction is
completed.
64 Fixed-Point Arithmetic Instructi ons
the R field. This byte is added to the effective byte and
then (if no memory protection violation occurs) the sum is
stored in
the effective byte location and the condition code
is set according to the value of the resultant byte. This
process
allows modification of a byte by any number in the
range -8 through +7, followed by a test.
If the value of the R field is zero, the effective byte is
tested for being a zero or nonzero value. The condition
code is set according to the result of the test, but the
effective byte is not affected. A memory write-protection
vioiation cannot occur in this case; however, a memory
read-protection violation can occur.
Affected: CC if (1)8-11 -I 0
(EBL) and CC if (1)8-11 10
If (1)8_11/0, EB + (1)8-11 SE - EBL and set CC
If (1)8-11 = 0, test byte and set CC
Condition code settings:
2 3 4 Result in EBL
- 0 0 0 Zero
- 0
o Nonzero
o No carry from byte
- Carry from byte
If MTB is executed in an interrupt or trap location, the
condition code is not affected and a 20-bit reference ad-
dress is used, as descri bed under "Interrupt and Trap Entry
Addressing
II, Chapter 2.
Note: All "Modify and Test" instructions in interrupt loca-
tions other than Counter 4 use real, or real extended,
addressing mode. Counter 4 uses virtual addressing
mode.
MTH
H
o 1 2
MODIFY AND TEST HALFWORD
t
(Halfword
index alignment)
3 1 4 5 6 7 8 9 10 11 12 13 ·14 15 16 17 18 19! 20 21 22 23 24 25 26 27128 29 30 31
If the value of the R field is nonzero, the high-order bit
of the R field (bit position 8 of the instruction word) is ex-
tended 12 bit positions to the left, to form a halfword with
bit positions 0-11 of that halfword equal to the high-order
bit of the R field. This halfword is added to the effective
halfword and then (if no memory protection violation oc-
curs) the sum is stored in the effective halfword location
and the condition code is sP,t according to the value of the
resultant halfword. The sum is stored regardless of whether
or not overflow occurs. This process allows modification of
a halfword by any number in the range -8 through +7, fol-
lowed by a test.

Xerox 550 Specifications

General

Brand	Xerox
Model	550
Category	Printer
Language	English