Advertisement
Explanation:
C
The
operation
or,
in
the
case
of the interruptible
instructions, the unit of operation is completed.
N
The operation or,
in
the
case
of
the
interruptible
instructions,
the
unit of operation is nullified.
The
instruction address in the old PSW has not been updated.
S
The operation or,
in
the
case
of
the
interruptible
instructions, the unit of operation is suppressed.
T
The execution of the instruction is terminated.
X
The event
is indicated with
the exception if the event
has
occurred; that is, the
contents
of the
monitored
storage location or general register were altered, or an
attempt was
made to execute an
instruction whose first
byte is located in the monitored area.
+
A model is permitted, but not
required, to indicate the
event if the event would have occurred had the operation
been completed but did not take place because the execu-
tion of the instruction was terminated.
2
The event is not indicated.
When an access exception applies to the second or
third
halfword
of
the
instruction but the first halfword is
accessible, it is unpredictable whether the instruction-
fetcning event is indicated.
This
condition
may occur in the case of the interrupt-
ible instructions when the event is
recognized
in
the
unit of operation that is completed and when the
excep-
tion causes the
next unit of operation to be suppressed
or null ified.
Indication of PER Events (Part 2 of 2)
Programming Notes
1. The execution of the interruptible instructions
MOVE LONG (MVCL) and COMPARE
LOGICAL LONG (CLCL) can cause events
for general-register alteration and instruction
fetching. Additionally, MVCL can cause the
storage-alteration event.
a.
The instruction-fetching event is indicat(
whe'never the instruction is fetched for
execution, regardless of whether it is the
initial execution or a resumption.
Since the execution of MVCL and CLCL
can be interrupted, a program event may be
indicated more than once. It may be necessary,
therefore, for a program to remove the
redundant event indications from the PER data.
The following rules govern the indication of the
applicable events during execution of these two
instructions:
b. The general-register-alteration event is
indicated on the initial execution and on
each resumption and does not depend on
whether or not the register actually is
changed.
c.
The storage-alteration event is indicated
only when data has been stored in the
monitored area by the portion of the
operation starting with the last initiation
and ending with the last byte transferred
Chapter 4. Control
4-15
Advertisement
Chapters
