Advertisement
r--------------,
1
1
I
r--------,
1
I
10Id PSW
1+-+---(1)-----,
I
l ________ J
I
I
I
1
I
1
r--------,
I
.-----------,
1
INew PSW 1--t---(2)---->ICurrent PSWI
I
l ________
J
I
l ___________
J
1
I
L ______________
J
Main Storage
Assuming that the instruction address
portion of a new PSW contains 1096, the
1st instruction after an interrupt would
be at location 1096.
By now you should realize these new
and old PSW·s are in fixed doubleword
locations in main storage.
Just where
are these locations?
The answer will
depend on just what class of interrupt
it is.
There are five distinct classes
of interrupts:
1.
External
2.
Supervisor
1-54
Can be caused by
pressing an interrupt
key on the operator's
console.
Caused by an instruc-
3.
Program
4.
Machine
5.
1/0
tion known as super-
visor call.
'':aused by a program
check.
Caused by a machine
check.
Caused by an Input-
Output operation.
Each of the above five class.es of
interrupts has its own main storage
locations for new and old PSW's as
follows:
Interrupt
External
Supervisor
Program
Machine
1/0
Old PSW
0024
0032
0040
0048
0056
New PSW
0088
0096
0104
0112
0120
For example a machine check causes the
PSW to be placed in location 0048 and a
new PSW to be brought out from location
0112.
Notice that these locations are
all divisible by eight since they con-
tain doublewords, and must reside on
doubleword boundaries.
Also, each new
Advertisement
