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Operation
some
confusion
results from the use of various terms
for the 990 computer
family front panels.
Front panel is a general term that includes the following items.
e
The control/display module described in this section
e
The programmer panel described in this section
e
The older operator panei that has a simple OFF-ON-LOAD switch and a minimal set of in-
dicators
The 990/10A contains a self-test routine to verify the proper operation of the processor before
loading the operating system. Self-test is normally executed on power-up as well as before loading.
The time required for self-test execution ranges from one to forty seconds. In addition, the load
device verification routine waits up to five minutes for the operator to provide a suitable load device.
In case of error, self-test results are displayed on the front panel indicators.
3.2
CONTROL/DISPLAY MODULE CONTROLS AND INDICATORS
The control/display
module
provided
with the computer
chassis
is fully explained
in the Model
990A13 Chassis Maintenance Manual, General Description.
This section provides a brief descrip-
tion of those controls and indicators necessary for normal operation with the 990/10A.
3.2.1
Controls
There are four switches of interest on the CDM. These switches are operational
if the security
switch is in the local position. The CDM is shipped with the switch in local; the remaining positions
are for service
only. The
security
switch
is concealed
by the chassis
bezel
when
the CDM
is
installed.
3.2.1.1
HALT Switch.
The HALT switch (Figure 3-1) suspends computer operation by forcing the
processor to service a nonmaskable interrupt and execute the front panel service routine contained
in the loader/self-test ROM. In this mode the HALT switch then signals a single instruction execu-
tion (SIE) which executes the interrupted program one instruction at a time. This feature is used and
explained in the discussion on self-test failures.
3.2.1.2
RUN Switch.
The RUN
switch commands
the processor to resume execution from the
point at which it was halted.
3.2.1.3
LOAD Switch.
The LOAD switch commands the processor to load from a TILINE device at
address > F800 unit 0. Each load begins with an RSET instruction to reset all TILINE devices.
3-2
2302633-9701
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