IBM System/360 Operating Guide

The IBM 1052 Printer-Keyboard is the basic con-
sole printer-keyboard for the System/360 Model 30.
Communication between operator and program is,
therefore, effected through the 1052. Besides the
1052, a variety of IBM 1050 console devices is
available to increase the flexibility of the system.
These devices (including the 1052) are attached to
the IBM 2030 Processing Unit through an IBM 1051
Control Unit and the 1051 Attachment feature, which
is located in the 2030.
The maximum number of 1050 console devices
attachable through this feature are:
• One keyboard
• Two printers
• One reader (either card or paper tape)
• One punch (either card or paper tape).
These devices can be operated separately from
the 2030 (even if CPU power is off) on a 24-hour
basis. Additional use-rental is not charged for the
2030 while the 1050 devices are used in this manner.
This type of operation is called off-line (off-line
Signifying that the 1050 devices are not being used
in operations that affect the 2030). Off-line opera-
tion provides for media conversion (such as trans-
ferring data from card to paper tape), card or paper
tape listing or preparation, and other 1050 operations
that do not depend on 2030 functions.
Interdependent operations between the 2030 and
the console devices are termed on-line operations.
An example is an operator request for information
from the 2030 by means of the IBM 1052 Printer-
Keyboard.
Additional flexibility is gained through a data
communications linle Here the local 1050 devices
(located near the 2030) can exchange information
with up to 26 remote 1050 terminals. This com-
munication link can be operated off-line only. That
is, messages sent and received by the local 1050
devices are not controlled and not sent or received
by the 2030. The local 1050 I/O devices not being
used in the data communications link can, however,
be operated on-line with the 2030. This operation
can occur at the same time as the off-line data
communications operation.
IBM 1052 PRINTER-KEYBOARD
To distinguish between data communications
operations and local operations we use the terms
line loop and home loop. Home loop 1050 device
operations can be on-line to the 2030 or off-line,
as already described, among the local 1050 devices.
Line loop refers to operations on the communications
line. These operations can occur only between
local 1050 devices and remote 1050 terminals that
all operate off-line to the 2030.
To summarize:
1. On-line refers to operations between devices
and the 2030.
2. Off-line refers to operations that do not involve
the 2030.
3. Home loop refers to operations on a local basis,
either on-line or off-line.
4. Line loop refers to communications line opera-
tions.
Because the usag"e of I/O devices can become criti-
cal in time-dependent applications, it is important
that the programmer fully understand the meanings
of the terms on-line and off-line.
Off-line line-loop operations require an IBM
1051 Modell Control Unit with the Master Station
feature. The 1051 Modell has two control unit
data loops:
1. One of these, called the home loop, can be
operated on-line or off-line to the 2030.
2. The other, called line loop, has data communi-
cation capabilities and can be operated only
off-line with respect to the 2030.
Local 1050 devices can be transferred to operate
on one loop.2.E.. the other (line loop or home loop)
by switches on the local units.
Multiplexor Channel Address
The unit address of the 1050 console is a fixed
multiplexor channel address. In a 2030 with 8,192
positions of main storage, the 1050 console address
is always IF (hexadecimal). System/360 Model 30
29

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English