Hitachi HIDIC MICRO-EH Applications Manual page 241

9.1.4 Relationship of Each Scan Type
When three types of scan occur at the same time, scan is executed in the order of periodical scan, then interrupt scan, and
then normal scan.
Periodical scan
Interrupt scan
Normal scan
Periodical system processing
10 ms periodical
Periodical
program
scan
20 ms periodical
program
40 ms periodical
program
Interrupt analysis
Interrupt
processing
scan
Interrupt program
INT16
INT17
INT18
:
:
INT27
Ladder program
Normal
END scan
scan
Processing
Interrupt label
INT0
INT1
INT2
INT16
INT17
INT18
INT19
Execution priority
Low
Normal scan Interrupt scan Periodical scan
10 ms
Figure 9.15 Relational diagram of scan operation
Table 9.3 List of interrupt label
Cause of startup
Interrupt every 10 ms
Interrupt every 20 ms
Interrupt every 40 ms
Interrupt of interrupt input 1
Interrupt of interrupt input 2
Interrupt of interrupt input 3
Interrupt of interrupt input 4
High
10 ms
Interrupt label
INT20 Counter 1 on-preset match
INT21 Counter 1 off-preset match
INT22 Counter 2 on-preset match
INT23 Counter 2 off-preset match
INT24 Counter 3 on-preset match
INT25 Counter 3 off-preset match
INT26 Counter 4 on-preset match
INT27 Counter 4 off-preset match
9-8
Chapter 9 PLC Operation
10 ms 10 ms
Cause of startup