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Mode Selector Switch (Continued)
ALTER MAR IRPT
This position of the MODE SELECTOR switch
allows you to alter the MAR for the current
interrupt level.
When altering this register for the display or
alter function, the initial contents of this regis-
ter must be noted. This register must be reini-
tialized to its original value before returning to
the microprogram.
With the switch in this position, the 16 binary
bits from the data switches 1, 2, 3, and 4 are
entered into the current MAR when the CE
START key is pressed. Data switch settings
are displayed in the display lights.
ALTER STOR
This position is used to alter the contents of
main storage or control storage. It is used with
the STOR SEL switch, MAR, and the data
switches.
The STOR SEL switch controls whether main
storage or control storage is accessed. MAR
contains the address of the location to be altered.
If main storage is being altered, the contents of
data switches 3 and 4 are stored in the addressed
location. If control storage is being altered, the
contents of data switches 1, 2, 3, and 4 are
stored. Data switch settings are displayed in the
display lights.
Pressing the CE START key initiates the alter
storage operation cycle. During this cycle the
address in MAR is increased by one. Thus, it
is possible to alter several sequential positions
of storage without entering a new address in
MAR each time.
DPLY STOR
This position is used to display the contents of
SO R, or the contents of main storage or con-
trol storage. When displaying main storage or
control storage, the switch is used with the STOR
SE L switch and MA
R.
Turning the MODE SELECTOR switch to this
position displays the current contents of SDR.
To display the contents of a location of main
storage or control storage, it is necessary to do
the following:
1.
Set the address in MAR of the location
you wish to display (alter MAR I RPT).
2.
Select main storage or control storage by
setting the STOR SE L switch.
3.
Turn the MODE SELECTOR switch to the
DPL Y STOR position; then press CE
START to initiate the operation.
During the storage cycle, which is initiated by
the CE START key, the contents of storage is
set into the SDR and displayed in the lights.
MAR is increased by one. Thus, sequential bytes
can be displayed without setting a new address
into MAR each time.
When control storage is displayed, all 18 bits
appear in the display lights. When main storage
is displayed, 9 bits are displayed in the low-
order byte of the display lights. The high-order
byte of the display lights are all on but mean
nothing.
INSN STEP/
° DPLY LSR
° ALTER STOR
° ALTER MAR
IRPT
° DPLY STOR
olNSN STEP/
DPLY CHKS
°INSN STEP/
°
DPLY peR
lsys
I NSN STEP
MODE SELECTOR
7-4
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