IBM System/360 Operating Guide

A system reset is initiated when the Load key
is pressed. The Basic Test microprogram is
looped 128 times. A microprogram (ROS) then
automatically resets the UC\V's in the multiplexor
storages. It mayor may not be necessary to clear
the contents of core storage into which the new
program is loaded; this is dependent upon the
program.
After the program has been loaded, processing
will proceed immediately unless the program
loaded is written in sue h a manner as to prevent
this. Therefore, system operating procedures and
the program determine what subsequent action is
to be taken. If the system is programmed to go to
the wait state after the program has been loaded,
operating procedures may indicate that the following
action is to be initiated:
1. Press the Stop key to enter stopped state (Manual
light on). Wait for the system light to turn off.
2. Load an instruction address from rotary switches
F, G, H, and J into IC (Instruction Counter) by
using the set-IC key (see IC in the Push buttons
section of this publication).
3. Press the start key to start processing at the
instruction address loaded.
DISPLAY INFORMATION FROM STORAGE
The contents of any byte of storage can be dis played
when the CPU clock is stopped (the Manual light on
the OCP is on) and the Allow-Write indicator (in
CPU status section of 2030 console--Part 2 of
Figure 3) is off. The Allow-Write indicator, when
on, indicates that a read-from-storage operation
has been completed but that the associated write
cycle has not been performed.
Procedure
The contents of any storage position can be dis-
played when the following procedure is used (assume
that the test light is out and normal program proc-
essing is in progress):
1. Press the stop key (lower left portion of 2030
console--Figure 2). The system stops after
the current instruction is processed, and all
pending interrupts have been serviced.
2. After the system stops, the allow-wrIte indi-
cator is off and the manual light is on.
20
3. Set the rotary display-storage-select switch
(switch E) to the MS or AS position (depending
upon whether Main Storage or Auxiliary Storage
is to be used in this operation). (See lower
portion of Figure 2.)
4. Place the address of the desired byte in rotary
switches A,B,C, and D (Figure 2).
Note: If a byte of auxiliary storage is to be displayed,
set rotary switch A to LS (for Local Storage) or to
the desired MPX (multiplexor) storage position.
If auxiliary is used, the address of the desired byte
is then set in switches C and D.
5. Press the display key (lower left section of
Figure 2).
6.
Make sure that the appropriate indicator, MAIN
STOR (main storage) or A UX STOR (auxiliary
storage), is on. These indicators are just to
the right of the main-storage address register
display (see Part 2 of Figure 3).
7. The address of the accessed location is then
displayed in the main-storage address register
(Part 2 of Figure 3). Make sure this is the
address desired. (You may inadvertently have
set up rotary switches A, B, C, and D incor-
rectly. )
8.
The data stored in the addressed location is
displayed in the main-storage data register
indicators on the 2030 console.
9. When the system and wait lights are on and the
stop key does not allow a display of storage,
the operator should set the rate switch to
SINGLE-CYCLE to turn off the system light
and turn on the manual light.
10. Only when all the preceding nine items fail,
should system reset be performed.
STORE INFORMATION INTO STORAGE
Store operations are similar to display operations.
That is, the contents of any poSition of storage can
be altered if the allow-write indicator is off and the
manual light is on (C PU clock stopped). If the
allow-write indicator is on or the manual light is
off, the store key (on OC P section of 2030 console,
see Figure 2) is interlocked so that the contents of
storage cannot be altered.
Procedure
To store a byte into storage:
1. When the system stops (stop key has been
pressed), the allow-write indicator is off and
the manual light is on.

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English