update reference which does not change
the contents of the location may occur
for that portion,if any, of the store
type operand for which no access excep
tion exists. The interlocked-update
referencecan occur only if the priority of the exception is equal to or lower
than the priority ofan access exception
forthe store-type operand.
When the exceptionis a specification
exception fora store-type operand which requires alignment on integral bounda
ries, the interlocked-updatereference which may occur is limited to the single
byte at the location designated by the
operand address.Programming Note The update appears to be an interlocked-update reference as observed
by otherCPUs. It is not interlocked as
observed by channels. Examples of when
an interlocked-updatereference may
occur to the destination-operand
location in storage are:• • Specification exception for an odd
register number forCOMPARE DOUBLE AND SWAP Data exception for an invalid deci
mal sign for ADDDECIMAL • Decimal-divide exception for DIVIDE DECIMAL DUAL-ADDRESS-SPACE CONTROL The dual-address-space (DAS) facility
consists ofa number of interrelated
functions. Some ofthese functions are described in this chapter, specifically
in the sections "DAS-Authorization Mech
anisms" and"PC-Number Translation."
Additionally, address spaces, ASN trans
lation, and ASN authorization are
described inChapter 3, "Storage"; DAS
tracingin Chapter 4, "Control"; inter ruptions in Chapter 6, "Interruptions"; and the instructions in Chapter 10, "Control Instructions."
A complete list ofthe functions,
control-register fields, and
instructions that are part of DAS is
included in Appendix D,"Facilities." SUMMARY These major functions are provided:
1.
2.
3.
4.
5.
6• Two address spaces for immediate
use bythe program
Means for changing to other spacesThree instructions for moving
information
A table-based
mechanism
subroutine-linkage
The use of multiple accesskeys for
key-controlled protection by prob
lem programs
Aids for program-problem analysis
Additionally, control and authority
mechanismsare incorporated to control
these functions.These functions are intended for use by
programs considered tobe semiprivileged, that is, programs which
areexecuted in the problem state but
which maybe authorized to use addi
tional capabilities. The authorization
mechanisms provided with DASare described in the section "DAS Authori
zationMechanisms" in this chapter.
The 11 instructions which are included
as part of DAS aredescribed in Chapter 10, "Control Instructions." DAS
includes the privileged instructionLOAD ADDRESS SPACE PARAMETERS and the follow
ingsemiprivileged instructions: EXTRACT PRIMARY ASN EXTRACT SECONDARY ASN INSERT ADDRESS SPACE CONTROL INSERT VIRTUAL STORAGE KEY MOVE TO PRIMARY MOVE TO SECONDARY t"OVE WITH KEY PROGRAM CALL PROGRAM TRANSFER
SET ADDRESSSPACE CONTROL SET SECONDARY ASN
In addition, when DAS is installed, two
instructions which are not part of DAS
are changed tobe semiprivileged. These
instructions are:INSERT PSW KEY
SETPSW KEY FROM ADDRESS
The changes to the operation of these
two instructions are under the control
of mode bits in thePSW or in control registers. Whenever a program in the
problem state attempts toexecute any of the 13 instructions at a time when the
required control registers have notbeen set up, a program exception is indicated which is also available on machines
without DAS.Chapter 5. Program Execution 5-13
the contents of the location may occur
for that portion,
type operand for which no access excep
tion exists. The interlocked-update
reference
than the priority of
for
When the exception
exception for
ries, the interlocked-update
byte at the location designated by the
operand address.
by other
observed by channels. Examples of when
an interlocked-update
occur to the destination-operand
location in storage are:
register number for
mal sign for ADD
consists of
functions. Some of
in the sections "DAS-Authorization Mech
anisms" and
Additionally, address spaces, ASN trans
lation, and ASN authorization are
described in
tracing
A complete list of
control-register fields, and
instructions that are part of DAS is
included in Appendix D,
1.
2.
3.
4.
5.
6
use by
Means for changing to other spaces
information
A table-based
mechanism
subroutine-linkage
The use of multiple access
key-controlled protection by prob
lem programs
Aids for program-problem analysis
Additionally, control and authority
mechanisms
these functions.
programs considered to
are
which may
tional capabilities. The authorization
mechanisms provided with DAS
zation
The 11 instructions which are included
as part of DAS are
includes the privileged instruction
ing
SET ADDRESS
In addition, when DAS is installed, two
instructions which are not part of DAS
are changed to
instructions are:
SET
The changes to the operation of these
two instructions are under the control
of mode bits in the
problem state attempts to
required control registers have not
without DAS.