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The Clear STaR (Stu rage) Switch
has four functions as
shown in Table 1. These four functions are enabled by first
holding CLEAR STOR down and then pressing START.
This dual action requirement prevellts accidental clearing of
main storage. Note in Table 1 that each clear storage function
is dependent on the positions of two console switches:
the mode switch and write storage protect bits switch.
The processor-controller cycles completely through all
main storage addresses during execution of each clear storage
function.
The PROG (Program) Load Switch
is used to load the first
1442 card or 1054 tape record into main storage. This first
card or tape record must contain instructions that initiate
the loading of the remaining cards or tape records. (The
processor-controller must be in run mode for p,rogram
operation.) Only one input device can be used for initial
program load (IPL) and it must be in ready status. The first
1442 on the system is used for IPL. The 1054 is used for
IPL if there is no 1442 on the system.
The first card or tape record is read into main storage
beginning at the location specified by the I-register. Normally,
RESET is pressed prior to pressing PROG LOAD. This resets
the I-register to 0000. After RESET is pressed, the I-register
may be manually altered to some address other than 0000.
This allows the first card or tape record to be placed at any
location in main storage.
In any case, the processor-controller branches to location
0000 to begin instruction execution after the first card or
tape record has been transferred to main storage. Therefore,
location 0000 should contain a valid instruction.
The Ready Light
being on indicates that the processor-
controller is in an operative condition.
The Power On Switch
is used to turn on the power supplies
within the processor-controHer.
Mode
WSPB
Function
Switch
Switch
1.
Store contents of data entry switches in all
core storage locations.
Storage-protect
bits are removed and parity is corrected as
Run
Yes
required because of bit removal.
If all
data entry switches are off, only parity
bits are left in storage.
2.
Store contents of data entry switches in
each core storage location that is
Run
No
unprotected. Locations having protect
bits are unchanged.
3.
Clear storage protect bits. All other data
remains unchanged.
Parity is
Display
Yes
automatically corrected in each word:
in storage.
4.
Search for par i ty errors. The P-C cycles
through storage until stopped by the
stop key or a parity error. The check
Display
No
stop switch must be on for a parity error to
cause a stop.
Table 1. Clear Storage Functions
The Puwer Off Switch
is used to turn off the power supplies
within the processor-controller.
The Power On Light
being on indicates that the processor-
controller power supplies are operative.
The Lamp Test Switch
applies lamp voltage to all console
lamps when it is pressed. It is used to verify operation of all
console lamps.
The Wait Light
being on indicates that the processor-
controiler is in the stopped or wait state. The Slopped or
POOWNER
1111
LAMP
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RUN
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ALARM
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Figure 2. Console Pushbutton Switches and Lights, Top Row
8
IBM 1800 Operating Procedures
I
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