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dr) ~5~ Field Engineering
Theory of Operation
Multiplexer Channel
( 60,000 and 70,000 Series)
SY27-2300-1
PREFACE Because Engineering Changes may periodically
obsolete portions of this manual, the latest level
logic diagrams should be used as the final authority.
This manual presents the fundamental concepts and
operational principles for the 2870, 2870A, and
2870B :Multiplexer Channels. The machine type Note: References in this manual to COD (Channel
suffix letters are determined by the system attach- Operation Diagram) and lOP (I/O Operation)
ment and channel serial numbers. The channel diagrams relate to diagrams contained in Field
designations are: Engineering Diagrams Manual, IBM 2870 Multi-
plexer Channel (60,000 and 70,000 Series),
System/360 models (not including the Model 195) SY27-2301.
2870 Ser. No. 60,000 and 60,002-69,999 Additionally, references to flowcharts (FC:XXX)
2870A Ser. No. 60,001 and 70,000 Series also appear throughout the text of this and other
chapters; these relate to the autocharts contained
System/370 models (including the System/360 in Volume 1 of the 2870 ALDIs.
Model 195)
2870B 70,000 Series Manuals associated with this publication are:
Field Engineering Diagrams Manual, IBM 2870
The information contained herein relates princi- Multiplexer Channel, SY27-2301.
pally to the 2870A as a basis for data presentation. Field Engineering Maintenance Manual, IBM
\\"hen the 2870 differs slightly from the description 2870 Multiplexer Channel, SY27-2302.
provided for the 2870A series machines, the differ-
ence is shown in parentheses with an asterisk (*).
For example, the 2870 has eleven (*seven) levels of
priority. It is assumed that the reader has a basic
knowledge of the System/360 and System/370 funda-
mentals of operation and standard I/O interface.
Second Edition (April 1973)
This is a reprint of SY27-2300-0 incorporating changes released in the following Technical
Newsletters:
SY22-691S (dated September 20, 1972)
SY22-6926 (dated February 22, 1973)
Changes are periodically made to the specifications herein; any such changes will be
reported in subsequent revisions or Technical Newsletters.
This manual has been prepared by the IBM System Products Division, Product Publications,
Dept. B97, PO Box 390, Poughkeepsie, N. Y. 12602. A form is provided at the back of
this publication for reader's comments. If the form has been removed, comments may
be sent to the above address.