KEYENCE Visual KV Series - Manual (Page 218)

3.2 Interrupt Processing
3-194
Visual KV
Series
3
Chapter 3 Interrupts
2008
SET or
2813
EI
#00000
DW
DM1940
2002
2002
EI
HSP
0000
(0000 to 0015)
(0500 to 0503)
3.2 Interrupt Processing
This section describes interrupt processing.
3.2.1 Interrupt Processing
Outline
Normally, a PLC processes a ladder sequence program by repeating the steps of
input processing, program execution, and output processing. Therefore, signals
which are shorter than the scan time cannot be received.
When the interrupt processing function is used, a process can be executed at the
instant of the interrupt, independent of the scan time.
When any interrupt occurs, the Visual KV series suspends the currently executed
program and executes the interrupt program in accordance with the interrupt factor.
When the interrupt program completes, the Visual KV resumes execution of the
suspended program.
➮ For more about scan time, refer to "1.1.2 Scan Time" (p. 3-3).
Direct input/output
The direct input/output functions are used during interrupt processing. Direct input
allows the KV PLC to fetch the input status of input relays 0000 through 0015 (KV-
10xx: 0000-0005, KV-16xx: 0000-0009) during execution of the interrupt program.
Direct output allows the Visual KV PLC to output the ON/OFF status of output relays
0500 through 0503 during execution of the interrupt program.
No special setting is required to use the direct input/output functions. The functions
can be used only by using the devices assigned for direct input/output within the
interrupt program.
Executing interrupts
The INT (Interrupt) instruction is used to execute an interrupt. Since an interrupt is
disabled at the start of operation, it is necessary to execute an EI (Interrupt enable)
instruction before using the INT instruction. In addition, the input time constant
should be set shorter by using the HSP instruction (to 10 µs) or by specifying the
desired value in DM1940 and turning ON special utility relay 2813.
➮ For more about the input time constant, refer to "1.4.1 Input Time Constant Change Function" (p. 3-
23).
Direct output
Input
processing
Program
execution
Output
processing
Scan
time
Interrupt input
Return to the next
line of the interrupt.
Interrupt
processing
Direct input *
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