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GF20-0385-0
Data
Processing An Introduction to
Techniques Microprogramming
This document describes some aspects of microprogram-
ming as it has been and is being used in certain IBM
processirig units. It is intended to provide a general
understanding of the subject.
To achieve this objective, the document has been divided
into two parts-Part I provides the reader with elementary
concepts: what microprogramming is, what it does, how it
is used, etc. This material is sufficient for the reader who
wishes only a broad understanding of microprogramming.
Part I requires ~o prerequisite knowledge by the reader
other than basic data processing concepts.
Part II is far more detailed and is intended to provide an
understanding of some microprogramming specifics.
While the System/370 Models 135 and 145 are used as
instructional devices, the material is not intended to be
a description of how, or through what vehicles, these
devices are microprogrammed. Part II requires close
attention to detail, and is for those who wish a more
explicit description than that provided by Part I. Part II
presumes some knowledge of assembler language program-
ming concepts as well as a basic familiarity with the
principles of complement arithmetic.
The document concludes with some recommendations for
further reading. IBM does not provide educational or
instructional manuals for any specific microprogrammable
device. However, the field engineering maintenance
documents peculiar to the device in question, as an adjunct
to their primary objective, may contain further details on
certain microprogram mabie aspects of that device.
CONTENTS
Part I
OverView . . . . . . . . . . . . . . . . . . . . 1
Simulation of Functions . . . . ......... . . . . . . .. 1
Microcode: The IBM System/360 . . . . . . . . . . . . .. 1
Read Only Storage . . .... . . . . ... 2
Writable Control Storage 2
System/370 . . . . . . . . . . ... 3
Special Features . . . . . . . . . . . . . 4
Considerations of Reloadable Control Storage .