Hitachi NJI-350B - Manual (Page 235)

Chapter 9 PLC Operation
9-2
9.1 RUN Start
When the MICRO-EH switches to the operating state, the user program is executed in sequence from the beginning. The
user programs consist of a normal scan program and periodical scan program. In addition to these programs, there is a
subroutine area defined as a subroutine.
Table 9.2 Program classification
No. Program classification Description Expression
1 Normal scan program This is the program that is normally executed.
When the program has been executed to the
END instruction, execution starts again from
the beginning.
Congestion error is monitored according to the
congestion check time set by the user. It is
monitored from the beginning of the program
to the END instruction.
When it is specified to continue during
congestion (R7C0), the operation continues
even if a congestion error occurs.
END
Normal scan
program
2 Periodical scan program This program is executed periodically at
intervals of 10 ms, 20 ms, or 40 ms.
INT0: Every 10 ms
INT1: Every 20 ms
INT2: Every 40 ms
Each execution cycle time becomes a
congestion error monitoring time.
When it is specified to continue during
congestion (R7C1), the periodical scan
program is suspended during operation.
Described in the area after the END
instruction.
RTI
INTn
n = 0, 1, 2
Periodic scan
program
3 Interrupt scan program When there is an input to the input terminal
assigned to the interrupt input, the interrupt
program (INT16 to INT19) corresponding to
that input starts up.
If another interrupt caused by the same factor
occurs during the execution of the interrupt
program, a congestion error occurs. When the
operation continuation at a congestion error
(R7C2) is specified, the same interrupt scan
program is run from the beginning again. Described in the area after the END
instruction
If the counter value exceeds the preset value, a
corresponding interrupt program (INT20 to
INT27) starts up according to the counter
number. Described in the area after the END
instruction
4 Subroutine This is a program called by the CALL
instruction. Described in the area after the END
instruction
RTS
SBn
n = 0 to 99
Subroutine
program
RTI
INTn
n = 16 to 19
Interrupt scan
program
RTI
INTn
n = 20 to 27
Interrupt scan
program