5.4.3
Example of Error Diagnosis
using the ISTACK
Fig. 5-3 illustrates the structure of the ISTACK in conjunction with the
interruptions that have occurred.
- The program execution level CYCLE (
OB 1
) is interrupted by an interrupt.
- Following this, the program processing level interrupt is activated and
OB 3
called.
- The occurrence of a timed interrupt means that the INTERRUPT level is
exited and the TIMED INTERRUPT level activated and
OB 13
processed.
- An incorrect addressing operation leads to the activaton of the ADF
level where
OB 25
is processed. In the error handling program, the user
has programmed a stop operation (STS) the CPU aborts program execution.
Before the final transition to the stop mode, a total of four different
program execution levels were interrupted. If you now display the ISTACK on
the PG, you will obtain a
four-level
ISTACK, at the top the ISTACK with
depth 01, with the ID of the
last
interrupted program execution level (=
ADF). You can page down through the ISTACK until you reach depth 04,
representing the CYCLE program execution level, which was interrupted
first
.
STS
ADF
STS
X
X
Depth 04
Program execution levels
ISTACK
Depth 03
Depth 02
Depth 01
CYCLE
TIMED INTERRUPTS
INTERRUPT
ADF
OB 1
OB 3
OB 13
OB 25
Fig. 5-3
Example of evaluating the ISTACK
Control Bits and Interrupt Stack
CPU 948 Programming Guide
C79000-G8576-C848-04
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Содержание CPU 948
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Страница 324: ...Examples of Parameter Assignment CPU 948 Programming Guide 7 18 C79000 G8576 C848 04 ...
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Страница 370: ...Addressable System Data Area CPU 948 Programming Guide 8 46 C79000 G8576 C848 04 ...
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Страница 404: ...Operations with the Base Address Register BR Register CPU 948 Programming Guide 9 34 C79000 G8576 C848 04 ...
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Страница 522: ...PG Functions via the S5 Bus CPU 948 Programming Guide 11 38 C79000 G8576 C848 04 ...
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Страница 546: ...List of Key Words CPU 948 Programming Guide Index 6 C79000 G8576 C848 04 ...