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94
Error Processing
Section 5-7
have higher execution requirements for demanding calculations or processing
and which task may not vary in execution speed.
The lower priority task 1 and 0 (command line) will be allocated to the single
time slot of routine 1. These tasks get less execution time and also the execu-
tion is depending on how many other low priority task are running.
If all running tasks have the same priority, the tasks will be allocated to all
available slots.
The following examples show the different allocations of the tasks.
Example 1: Tasks 1 & 3 and command line task 0 running
The task 3 is allocated two time slots each millisecond. The other time slot is
equally allocated to the other tasks over multiple cycles.
Example 2: Tasks 1,2 & 3 and command line task 0 running
Both high priority tasks (3 and 2) are allocated to the two time slots. The other
time slot is equally allocated to the other tasks over multiple cycles.
5-7
Error Processing
For the safety of the application it is very important that proper safety mea-
sures are taken for the different problems which may occur in the system. For
safe operation at all times the user must make use of the several options to
check for these errors in both the MC Unit and Servo Driver.
As for the MC Unit, the BASIC programming language provide the program-
mer with the freedom to include a lot of safety measures or not. This requires
a sensible solution, which covers all possible behaviour of the system.
This section will present the possible errors that may occur and suggest the
way to detect them. For a full description of the error handling refer to section
8-2 Error Handling.
!Caution
The MC Unit outputs may have undefined status due to deposits on or burn-
ing of the output relays, or destruction of the output transistors. As a counter-
measure for such problems, external safety measures must be provided to
ensure safety in the system.
BASIC Errors
If a BASIC error is generated during the execution of a BASIC command in
some task, the program will be halted immediately or the user can define a
specific error routine structure to stop the system. The error routine can stop
the driver, put the digital I/O in a safe status and notify the PC Unit of the
error. Please refer to section 6-3-31 BASICERROR on the way to include an
error subroutine in a BASIC program.
Motion Error
In case a motion error occurs, the MC Unit will disable the control of the driver
automatically. The user has the ability to decide for each axis which motion
errors will disable the driver by using the ERRORMASK parameter (see sec-
tion 6-3-67 ERRORMASK). After detection of the motion error the user is free
to program the necessary countermeasures for the other axes and the com-
plete system.
Host Link Master
The Host Link Master protocol uses the HLM_STATUS parameter to define
the different error states. The HLM_STATUS parameter will contain error
states like Timeout and invalid Host Link strings received from the master.
The required actions such as a re-try for the error states are required to be
1 ms
1 ms
Task 0
Task 3
Task 3
Task 1
Task 3
Task 3
1 ms
1 ms
Task 0
Task 3
Task 2
Task 1
Task 3
Task 2