and stopped states. The key is not effective when the CPU is in the check-stop state.
Start Key
Activating the start key causes the CPU to enter the
operating state. See "Stopped and Operating States" in the chapter "System Control." The key is effec­
tive only when the CPU is in the stopped state, and
the effect is unpredictable when the stopped state
has been entered by reset.
Stop Key
Activating the stop key causes the CPU to perform
the stop function. See "Stopped and Operating States" in the chapter "System ControL" The stop key is effective only while the CPU is in
the operating state.
Operation Note
Activating the stop key has no effect when a contin­
uous string of interruptions occurs, when the prefix
register contains an invalid address, or when the CPU is unable to complete an instruction because of
a machine malfunction.
Store-Status Key
Activating the store-status key initiates the store­
status function. Although the store-status function is
performed compatibly on all models, the initiation of
the function differs among models. Some models
initiate the function by the use of a special keyboard
mnemonic and some by the use of a pushbutton,
while others may provide a CRT -menu selection. See "Store Status" in the chapter "System Con­ trol" for a description of the function.
The manual control for performing store status is
effective only when the CPU is in the stopped state.
Operation Note
The store-status function would ordinarily be used in
conjunction with a standalone ,dump program for the
analysis of program malfunctions. For such an oper­
ation, the following sequence would be called for: • Activating of the system-reset key. • Initiation of the store-status function. • Normal IPL of a standalone dump program.
System Indicator
The system indicator is on when the CPU cluster
meter or customer-engineer meter is running.
System-Reset Key
Activating the system-reset key causes a reset func­
tion to be performed. Whether the enable-system­
clear key is activated at the same time determines
the type of reset and the resultant effect on the sys­
tem. In a multiprocessing system, the effect of the
key is propagated to all CPUs configured, for reset
purposes, to this CPU. See the detailed discussion
under "Resets" in the chapter "System Control." Activating the system-reset key may change the
configuration, including the connection with chan­
nels, storage units, and other CPUs. The key is effective while power is on the system.
Test Indicator
The test indicator is on when a manual control is not
in its normal position or when a maintenance func­
tion is being performed for the CPU, channels, or
storage.
The test indicator is on whenever a control on the
system control panel or on any separate maintenance
panel for the CPU, storage, or channels is in an ab­
normal position that can affect the normal operation
of a program.
The test indicator may be on when one or more
diagnostic functions under control of DIAGNOSE are activated or when certain abnormal circuit­
breaker or thermal conditions occur.
The test indicator does not reflect the state of
marginal voltage controls.
Thermal/CB Power-Check Indicator
The thermal! CB power-check indicator, which is
one or more red lights, goes on when a thermal con­
dition, a circuit-breaker-trip condition, or both con­
ditions are detected in the CPU complex. This indi­
cator is turned off from the customer-engineer
power-control panel. TOD Clock Key
The TaD (time-of-day) clock key provides an inter­
lock in the execution of the instruction SET CLOCK for the purpose of guarding against an unauthorized
or inadvertent change to the time-of-day clock val­
ue.
When the TaD clock key is not activated, that is,
is in the position labeled "secure," the value of the
TaD clock is protected against alteration by the
program, and the execution of SET CLOCK does
not change the value of the clock.
When the TaD clock key is activated, that is, is in
the position labeled "enable set," alteration of the
clock value by means of SET CLOCK is permitted.
System Console 247

The key is situated between the power-on key
and the power-off key. It is spring-loaded, with the
spring restoring the key to the secure position.
In a multiprocessing system, the TOD clock is
secure only when the TOD clock on this CPU and
the keys on all CPUs configured to this CPU are in
the secure position. The TOD clock in each CPU of
a multiprocessing configuration is enabled for setting
when th,e TOD clock key on that CPU, or on any CPU configured to it, is in the enable-set position.
Wait lndicator
The wait indicator is on when the CPU is in the wait
state. Operation Note
The wait indicator, manual indicator, and system
indicator may be used by the operator to determine
the status of the system. The following table shows
the possible conditions when power is on and the CPU is not in the load or check-stop states.
Remote Operator-Control Panel
In some models, a remote operator-control panel (ROCP) is provided. The remote operator-control M9nual Indicator
1 System I ndicator
2
Wait Indicator off off off off off on off on off
off on on
on off off
on off on
on on off
on on on Explanation: * Abnormal condition.
panel functions are effective concurrently with those
on the system console. The settings of the load-unit­
address controls on the remote panel are selected if
the load key on the remote panel is activated.
Customer-Engineer Section
The customer-engineer section of the system control
panel contains controls intended only for customer­
engineer use.
Operation Note
Improper use of the customer-engineer-section con­
trols may, among other things, result in false
machine-check indications or cause actual machine
malfunctions to be ignored. It may also alter other
aspects of system operation, including instruction
execution and channel operation, to the extent that
the operation does not comply with that specified in
this manual. While the abnormal setting of such con­
trols causes the test indicator to be turned on in this CPU, in a multiprocessing system the operation of
another CPU may be affected even though its test
indicator is not turned on.
CPU State State of I/O System
3 Operating, Wait Not working
Operating Undetermined
Operating, Wait Working Stopped Not working Stopped, Wait Not working
Stopped Working
Stopped, Wait Working
1 The manual indicator may be off in some models while display-and-enter
operations are being performed.
2 When the system indicator is turned on, it remains on for a minimum of appro):imately one second.
3 The operation of the console device is included here as an I/O operation. In a
multiprocessing system, the system indicator may be on because of activity in
anothe'r CPU. When this is the case, the state of I/O system in undetermined.
System Status Indications
248 System/370 Principles of Operation