NAME
Emergency Pull Power On Power Off Interrupt
Wait
Manual System Test
Load
Load Unit Load Prefix Select\) (I< Multisystem feature
Emergency Pull Switch IMPLEMENTATION Pull switch
Key, backlighted
Key
Key
Light
Light
Light
Light
Light
Three rotary switches
Key
Key switch Pulling this switch turns off all power beyond the
power-entry terminal on every unit that is part of the
system or that can be switched onto the system. There­
fore, the switch controls the system proper and all
off-line and shared control units and 110 devices.
The switch latches in the out position and can be
restored to its in position by maintenance personnel
only.
When the emergency pull switch is in the out po­
sition, the power-on key is ineffective. Power-On Key
This key is pressed to initiate the power-on sequence
of the system.
As part of the power-on sequence, a system reset is
performed in such a way that the system performs no
instructions or 110 operations until explicitly directed.
the contents of main storage, including its protection
keys, remain preserved.
The power-on key is backlighted to indicate when
the power-on sequence is completed. The key is ef­
fective only when the emergency pull switch is in its
in position. Power-Off Key
The power-off key is pressed to initiate the power-off
sequence of the system.
The contents of main storage and its protection keys
are preserved.
Interrupt Key
The interrupt key is pressed to request an external
interruption.
The interruption is taken when not masked off and
when the CPU is not stopped. Otherwise, the inter­
ruption request remains pending. Bit 25 in the inter­
ruption-code portion of the current psw is made one
to indicate that the interrupt key is the source of the
external interruption.
Wait Light
The wait light is on when the CPU is in the wait state. Manual Light
The manual light is on when the CPU is in the stopped
state. Several of the manual controls are effective only
when the CPU is stopped, that is, when the manual
light is on. System Light
The system light is on when the CPU cluster meter or
customer-engineering meter is running.
Programming Note
The states indicated by the wait and manual lights
are independent of each other; however, the state of
the system light is not independent of the state of
these two lights because of the definition of the run­
ning condition for the meters. The following table
shows possible conditions. SYSTEM MANUAL WAIT CPU I/O LIGHT LIGHT LIGHT STATE STATE
off off off Not allowed when power is on
off off on Waiting Not operating
off on off Stopped Not operating
off on on Stopped, Not operating
waiting
on off off Running Undetermined
on off on Waiting Operating
on on off Stopped Operating
on on on Stopped, Operating
waiting
Test Light
The test light is on when a manual control is not in
its normal position or when a maintenance function is
being performed for CPU, channels, or storage.
Any abnormal switch setting on the system control
panel or on any separate maintenance panel for the CPU, storage, or channels that can affect the normal
operation of a program causes the test light to be on.
The test light may be on when one or more diag­
nostic functions under control of DIAGNOSE are acti­
vated or when certain abnormal circuit breaker or
thermal conditions occur.
The test light does not reflect the state of marginal
voltage controls.
Load Light
The load light is on during initial program loading;
it is turned on when the load key is pressed and is
turned off after the loading of the new psw is com­
pleted successfully.
Load-Unit Switches
Three rotary switches provide the II-bit address of
the device to be used for initial program loading. System Control Panel 119

The leftmost rotary switch has eight positions label­
ed 0-7. The other two are 16-position rotary switches
labeled with the hexadecimal characters 0-9, A-F.
Load Key
The load key is pressed to start initial program load­
ing, and is effective while power is on the system. Prefix-Select Key Switch
The prefix-select key switch provides the choice be­
tween main prefix and alternate prefix during manu­
ally initiated initial program loading.
The setting of the switch determines the state of the
prefix trigger following the system reset after the load
key is pressed.
The switch is part of the multisystem feature.
Operato,' Intervention Section
This section of the system control panel contains the
controls required for the operator to intervene in nor­
mal programming operation. These controls may be
intermixed with the customer engineering controls,
and additional switch positions and nomenclature may
be included, depending on the model. Operator intervention provides the system-reset and
the store-and-display functions. Compatibility in per­
forming these functions is maintained, except that the
word size used for store and display depends on the
physical word size of storage for the model. Switches
for display of the instruction address are absent on
models that continuously display the instruction ad­
dress.
The following table lists all intervention controls by
the names on the panel or controls and describes them.
NAME System Reset Stop Rate Start Storage Select Address
Data Store Display Set IC
Address Compare
Alterna te Prefix Multisystem feature
System-Re!;et Key
IMPLEMENT A TI ON Key
Key
Rotary switch
Key
Rotary or key switch
Rotary or key switches
Rotary or key switches
Key
Key
Key
Rotary or key switches
Light
The system-reset key is pressed to cause a system re­
set; it is effective while power is on the system. The
reset function does not affect any off-line or shared
device. 120 Stop Key
The stop key is pressed to cause the CPU to enter the
stopped state; it is effective while power is on the sys­
tem.
Programming Note Pressing the stop key has no effect when a continuous
string of interruptions is performed or when the CPU is unable to complete an instruction because of ma­
chine malfunction. The effect of pressing the key is
indicated by the turn-on of the manual light as the CPU enters the stopped state.
Rate Switch
This rotary switch indicates the way in which instruc­
tions are to be performed.
The switch has two or more positions, depending
on model. The vertical position is marked PROCESS. In
this position, the system starts operating at normal
speed whcn the start key is pressed. The position
left of vertical is marked INSTRUCTION STEP. When the
start key is pressed with the rate switch in this po­
sition, one complete instruction is performed, and all
pending, not masked interruptions are subsequently
taken. The CPU next returns to the stopped state.
Any instruction can be executed with the rate
switch set to INSTRUCTION STEP. Input/output opera­
tions are completed to the interruption point. When
the CPU is in the wait state, no instruction is per­
formed, but pending interruptions, if any, are taken
before the CPU returns to the stopped state. Initial
program loading is completed with the loading of the
new psw before any instruction is performed. The
timer is not updated while the rate switch is set to INSTRUCTION STEP. The test light is on when the rate switch is not set
to PROCESS. The position of the rate switch should be changed
only while the CPU is in the stopped state. Otherwise unpredictable results occur.
Start Key
The start key is pressed to start instruction execution
in the manner defined by the rate switch. Pressing the start key after a normal stop causes in­
struction processing to continue as if no stop had oc­
curred, provided that the rate switch is in the PROCESS or INSTRUCTION-STEP position. If the key is pressed
after a system reset, the instruction designated by the
instruction address in the psw is the first instruction
executed. In some models, the start key cannot be
pressed after a system reset until a new instruction
address or psw is introduced by pressing the set IC or
load switch.