Danaher Motion
06/2005
Error Handling
M-SS-005-03 Rev
E
159
11.1.1.2.
T
RY
/F
INALLY
Unlike an
OnError
block, the
Try/Finally
block may appear anywhere in the
main program section of the task. It can be used to take specific action with
relation to a particular area of your program code. This type of error handler
block only traps synchronous errors in the task context. The block is started
using the
Try
keyword and is terminated with the
End Try
keyword.
Try
blocks can be nested. The program lines between the line causing the
error and the matching catch statement are skipped. The interpreter tries to
trap an error starting with the innermost catch statement. If there is no
matching catch statement, the error is handled as a regular synchronous
error. Errors trapped inside the
Try
block are not logged. The
Finally
statement is executed only if an error occurred and was caught inside the
Try
block.
11.1.2. System
Context
System context is the lowest level of the three contexts. It refers to errors not
directly related to specific tasks. Errors that occur in this context affect all
running tasks. The default system error handler processes these errors.
Examples of system context errors include Floating Point Unit errors, CPU
errors, SERCOS communication errors and errors that occur on motion
elements not attached to specific tasks.
11.1.2.1.
O
N
S
YSTEM
E
RROR
OnSystemError
traps and processes all errors in the system context. It is the
upper-level of the hierarchical error processing structure formed by the
combination of
Try
,
OnError
and
OnSystemError
.
OnSystemError
may be
written in the body of any task, but only one instance may exist in the system
at any time. It traps both synchronous and asynchronous errors in all tasks,
as well as errors that occur within the context of the system.
A system error is not associated with a specific task. An example of a system
error is a position following error that occurs due to some external force
being applied to an axis not attached to a task. When an error is trapped, the
specified error processing code runs and the task is stops. The task is in
state 4. It is possible to continue task execution by explicitly entering
CONTINUETASK
within the error processing code, but the task continues
only after the error has been corrected.
OnSystemError
traps errors not specifically trapped by
Try
or by
OnError
. It
then executes either an orderly shutdown of the system, or an orderly
recovery procedure.
11.1.2.2.
E
RROR
P
RINT
L
EVE
L
SYSTEM.ERRORPRINTLEVEL
controls which types of system errors are
printed to the message log window. There are four levels of system errors:
fatal faults, errors, and notes.
0 (SILENTLEVEL) – Notes, errors, and fatal faults are not printed.
1 (FAULTLEVEL) – Notes and errors are not printed. Fatal faults are printed.
2 (ERRORLEVEL) – Notes are not printed. Errors and fatal faults are printed.
3 (NOTELEVEL) – Notes, errors, and fatal faults are printed.
