o Multiplexor channel mask
1 Selector c:hannel 1 mask
2 Selector c:hannel 2 mask
3 Selector channel 3 mask
4 Selector c:hannel 4 mask
5 Selector c:hannel 5 mask
6 Selector c:hannel 6 mask
7 External mask
8-11 Protection key
12
13 Machine check mask (M)
14 Wait state (W)
15 Problem state (P)
16-31 Interruption code
32-33
36-39 Program mask
36 Fixed-point overflow mask
37 Decimal overflow mask
38 Exponent underflow mask
39 Significance mask
Figure 14.
state as a result of conditions external to the system,
in input/output
classes of interruption conditions are possible:
Each class has two related psw's called
In all classes, an interruption involves merely storing
the current psw in its
psw at the
conclusion of the interruption routine, there is an
system is lrestored to the state prior to the interruption
and the interrupted routine continues.
Address length Purpose
o
72
76
84
88
* The size of
particular
16
Interruptions are
ruptable for the interruption source. The system mask,
program mask, and machine check mask bits in the
psw may be used to mask certain interruptions. When
masked off, an interruption either remains pending or
is ignored. The system mask
cause four of the 15 program interruptions to be
An interruption always takes place after one
of an interruption may affect the execution of the
following an interruption, the cause of the interrupt
ion is identified and provision is made to locate the
last executed instruction.
An
An
channel is not masked. The address of the channel
and
Further information concerning the
during the interruption.
Program Interruption
Unusual conditions encountered in a program create
program interruptions. These conditions include
as exceptional results. The interruption code identifies
the interruption cause. Figure 16 shows the different
causes that may occur.
Interruption Program Interrupti on
Code Cause
1
2
3
4
6
7
8
9
11
12
13
14
15
Figure 16. Interruption