Chapter 6 Applied Instructions
6-145
API
Instruction code Operand Function
0501 EI
－
Enabling the interrupt
Pulse instruction
16-bit instruction (1 step)
32-bit instruction
AH500
Symbol:
Explanation:
1. The use of the instruction EI indicates that the interrupt task is allowed to be used in the
program. (Please refer to section 6.6 in AH500 Operation Manual for more information about
task I0~task I255.)
2. The interrupt task is allowed to be used between the instruction EI and the instruction DI in the
program. When there is no part of the program in which the interrupt is disabled, users can
choose not to use the instruction DI.
3. During the execution of one interrupt task, other interrupts generated will not be executed, but
will be memorized. Not until the execution of the present interrupt task is complete will the next
interrupt task be executed.
4. When several interrupts occur, the interrupt task which should be executed first has higher
priority. When several interrupts occur simultaneously, the interrupt task whose pointer number
is smaller is executed first.
5. When the interrupt task occurring between DI and EI can not be executed immediately, the
interrupt request is memorized once, and the interrupt task is executed in the part of the
program in which the execution of the interrupt task is allowed.
6. When the immediate I/O signal is required in the execution of the interrupt task, users can use
the instruction REF in the program to refresh the state of the I/O.
Example:
If the PLC runs and the part of the program Cyclic_0 between the instruction EI and the instruction
DI is scanned, the interrupt task is executed when it is enabled. When the execution of the interrupt
task is complete, the main program is executed.
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