CHAPTER 12. OPERATOR FACILITIES
Manual Operation ••••••••••••••••••••••••.••••••••••••••••• 12-1
Basic Operator Facilities •••••••••••••••.••••••••••••••••• 12-1
Address-Compare Controls ••••••••••••••.••••••••••••••••. 12-1
A I ter-and-D i splay Cont ro Is ••...•.•••••.•••••••...••.•••• 12-2 Check-Stop Indicator •••• •••••••••••••.••••••••••••••••• 12-2
IML Control s ••.•••••••••••••.•••••••••.•.••••••••••••••• 12-2
Interrupt Key ...••••••••••••.•.•.•••••.••••••••••••••••• 12-2
Interval-Timer Control •••••••••••••••..••••••••••••••••• 12-3
Load Indicator •••••••••••••••••••••••••••••••••••••••••• 12-3
Load-Clear Key ••••••••••••••.•••••••••.••••••••••••••••• 12-3
Load-Normal Key ...••••.•••••••••••••••.••••••••••••••••• 12-3
Load-Unit-Address Controls ••••••••••.•.•.•••.••••••••••• 12-3
Manual Indicator ••••••••••••••••••••••.••••••••••••••••. 12-3
Power Controls ..•.••.•••.•••.•••••••••.•••••••.••••••••• 12-3
Rate Control ••.•••••...•.•••.•..••.•.•.••••••••••••••••• 12-4
Resta rt Key ••••.••••••.•••••••••••••...•.•.•••••......•. 12-4
Sta rt Key •••••.•••...•••••••.•••••••••.•.•••••••.••••••• 12-4
stop Key •...••.••••..••••.•.••••••.•••.••••••.•••••••••• 12-4
Store-Status Key .••..•...•••••••.•••••.•.••••..••••••••• 12-5
System-Reset-Clear Key ...•.•.•.•.•.•••.•••••..••••••.••• 12-5
System-Reset-Normal Key ..•.•••.•..••••.•..•.••..•••.••.• 12-5
Test Indi cator ••.••••.••••••••••••••••.••••••••••••.•••• 12-5 TOO-Clock Control .•••.•.••••.•.•••••••.••••••••••••••••• 12-5
Wai t Indi cator ....•.....••••.•••••••••.•.••••••••••••••• 12-6
Multiprocessing Configurations ••••••••••.•••••••••••••••.. 12-6
MANUAL OPERATION The operator facilities provide func­
tions for the manual operation and
control of the machine. The functions
include operator-to-machine communi­
cation, indication of machine status,
control over the setting of the TOO clock, initial program loading, resets,
and other manual controls for operator
intervention in normal machine
operation.
A model may provide additional operator
facilities which are not described in
this chapter. Examples are the means to
indicate specific error conditions in
the equipment, to change equipment con­
figurations, and to facilitate mainte­
nance. Furthermore, controls covered in
this chapter may have additional
settings which are not described here.
Such additional facilities and settings
may be described in the appropriate
System Library publication.
Most models provide, in association with
the operator facilities, a console
device which may be used as an I/O device for operator communication with
the program; this console device may
also be used to implement some or all of
the facilities described in this
chapter. The operator facilities may be imple­ mented on different models in various
technologies and configurations. On some models, more than one set of phys­
ical representations of some keys,
controls, and indicators may be
provided, such as on multiple local or
remote operating stations, which may be
effective concurrently.
A machine malfunction that prevents a
manual operation from being performed
correctly, as defined for that
operation, may cause the CPU to enter the check-stop state or give some other
indication to the operator that the
operation has failed. Alternatively, a
machine malfunction may cause a
machine-check-interruption condition to
be recognized. BASIC OPERATOR FACILITIES ADDRESS-COMPARE CONTROLS The address-compare controls provide a
way to stop the CPU when a preset address matches the address used in a
specified type of main-storage refer­
ence. One of the address-compare controls is
used to set up the address to be
compared with the storage address. Chapter 12. Operator Facilities 12-1

Another control provides at least two
positions to specify the action, if any,
to be taken when the address match
occurs:
1. The normal position disables the
address-compare operation.
2. The stop position causes the CPU to enter the stopped state on an
address match. When the control is
in this setting, the test indicator
is on. Depending on the model and
the type of reference, pending I/O, external, and machine-check inter­
ruptions mayor may not be taken
before entering the stopped state.
A third control may specify the type of
storage reference for which the address
comparison is to be made. A model may
provide one or more of the following
positions, as well as others:
1. The any position causes the address
comparison to be performed on all
storage references.
2. The data-store position causes
address comparison to be performed
when storage is addressed to store
data.
3. The I/O position causes address
comparison to be performed when
storage is addressed by a channel
to transfer data or to fetch a
channel-command or indirect-data­
address word. Whether references
to the channel-address word or the
channel-status word cause a match
to be indicated depends on the
model.
4. The instruction-address position
causes address comparison to be
performed when storage is addressed
to fetch an instruction. The
rightmost bit of the address
setting mayor may not be ignored. The match is indicated only when
the first byte of the instruction
is fetched from the selected
location. It depends on the model
whether a match is indicated when
fetching the target instruction of EXECUTE. Depending on the model and the type of
reference, address comparison may be
performed on virtual, real, or absolute
addresses, and it may be possible to
specify the type of address.
In a multiprocessing configuration, it
depends on the model whether the address
setting applies to one or all CPUs in
the configuration and whether an address
match causes one or all CPUs in the
configuration to stoP.
12-2 System/370 Principles of Operation ALTER-AND-DISPLAY CONTROLS The operator facilities provide controls
and procedures to permit the operator to
alter and display the contents of
locations in storage, the storage keys,
the general, floating-point, and control
registers, the prefix, and the PSW.
Before alter-and-display operations may
be performed, the CPU must first be
placed in the stopped state. During
alter-and-display operations, the manual
indicator may be turned off temporarily,
and the start and restart keys may be
inoperative.
Addresses used to select storage
locations for alter-and-display oper­
ations are real addresses. The capabil­
ity of specifying logical, virtual, or absolute addresses may also be provided. CHECK-STOP INDICATOR The check-stop indicator is on when the CPU is in the check-stop state. Reset
operations normally cause the CPU to
leave the check-stop state and thus turn
off the indicator. The manual indicator
may also be on in the check-stop state.
IML CONTROLS The IML controls provided with some
models perform initial microprogram
loading (IML).
The IML controls are effective while the
power is on.
Note: The name "IMPL controls" was used
in earlier descriptions. INTERRUPT KEY When the interrupt key is activated, an
external-interruption condition indicat­
ing the interrupt key is generated.
(See the section "Interrupt Key" in Chapter 6, "Interruptions.")
The interrupt key is effective when the CPU is in the operating or stopped
state. It depends on the model whether
the interrupt key is effective when the CPU is in the load state.