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01-0001
" =1
Set ROAR
o
ROAR Go
o
~SA~L~Go~od~
_______
L-~OO~OO~.~··LI
- L _ _
~0~OO~1
__
SL~
__
~01~03
__
~-L~
____
~
____
J-~
__
~0~104~~~
__
~0~OO~1
__
- L - L _ _
~00~02_~
C
R F'NX
-+-
WX
R
Figure 3-44.
Micro Program Break-In
0001
L
Cycle 0000
is executed, the 6 and 7 positions of
the S-register could be changed.
At T1 of this cycle, the address of the
next micro program step, 0001, is set
into ROAR.
At T2 time, the GO pulse
causes the data at address 0001 to be
read out to the SAL'S.
The SAL'S are
good during T4 time.
Assume that during
T4 time, a micro program break-in is
called for.
Because of this
int~rrup
tion, the address in ROAR, 0001, is
stored in a backup storage address reg-
ister (ROBAR).
Dead Cycle
This is called a dead cycle because no
control latches are set.
The set pulse
to the latches is blocked fo.r the first
cycle of the interruption.
This should
have been the time the control latches
were set for address 0001.
At T1 time
of this cycle, a new address (0103) is
forced into ROAR.
This address is the
first step of the alternate rricro pro-
gram to handle the interruption.
Also at this time, the branch condi-
tions for address 0001 are set into
backup X6 and X7 latches.
The branch
conditions, S6 and S7, have been tested
by the SAL's that are good for
address 0001.
Their status must be
stored because, as the alternate program
Cycle 0103
This is a normal cycle that executes the
ROS word at address 0103.
Set Up Cycle
This cycle is a normal cycle before the
last step in the alternate routine.
Its
only function in this example is to set
ROAR with the address 0104 and begin
execution of this ROS word.
Cycle 0104
During this cycle, the control-register
latches are good for address 0104.
At
T1 time, it ib necessary to set ROAR
with the next address to be executed.
Since this is the last step of the
altt:rnate routine, the address in backup
ROAR, 0001, is gated to ROAR so that the
original micro program that was inter-
rupted may be resumed.
ROAR Restore Buffer Latch
This latch is turned on at T2 time when
a statement in the micro program speci-
fies that ROAR must be changed.
This
statement appears in the last step of
3-65
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