5: S
PECIAL
F
UNCTIONS
FC5A M
ICRO
S
MART
U
SER
’
S
M
ANUAL
FC9Y-B1268
5-35
Example: Interrupt Input
The following example demonstrates a program of using the interrupt input function, with input I2 designated as an
interrupt input. When the interrupt input is turned on, the input I0 status is immediately transferred to output Q0 using
the IOREF (I/O refresh) instruction before the END instruction is executed. For the IOREF instruction, see page 11-9
(Advanced Vol.).
M8120 is the initialize pulse special internal relay.
D8032 stores 0 to designate jump destination label 0 for interrupt input I2.
The interrupt program is separated from the main program by the END instruc-
tion.
When input I2 is on, program execution jumps to label 0.
M8125 is the in-operation output special internal relay.
IOREF immediately reads input I0 status to internal relay M300.
M300 turns on or off the output Q0 internal memory.
Another IOREF immediately writes the output Q0 internal memory status to
actual output Q0.
Program execution returns to the main program.
Insert LRET at the end of the subroutine to return to the main program.
LABEL
0
M8120
END
Main Program
M8125
Q0
REP
S1 –
0
D1 –
D8032
MOV(W)
IOREF
S1
I0
M300
M8125
IOREF
S1
Q0
LRET
Notes for Using Interrupt Inputs and Timer Interrupt:
When using an interrupt input or timer interrupt, separate the interrupt program from the main program using the END instruction
at the end of the main program.
When an interrupt program calls another subroutine, a maximum of 3 subroutine calls can be nested. If more than 3 calls are nested,
a user program execution error occurs, turning on special internal relay M8004 and the ERR LED.
When using an interrupt input or timer interrupt, include the label number of the interrupt program to be executed when an inter-
rupt occurs. The label numbers stored in data registers D8032 through D8036 specify the interrupt programs for interrupt inputs I2
through I5 and timer interrupt, respectively.
When more than one interrupt input is turned on at the same time, interrupt program execution is given priority to inputs I2, I3, I4,
and I5, in that order. If an interrupt is initiated while another interrupt program is executed, the subsequent interrupt program is exe-
cuted after the prior interrupt is completed. Multiple interrupt programs cannot be executed simultaneously.
Make sure that the execution time of the interrupt program is shorter than interrupt intervals sufficiently.
Interrupt programs cannot use the following instructions: SOTU, SOTD, TML, TIM, TMH, TMS, CNT, CDP, CUD, SFR, SFRN, WKTIM,
WKTBL, DISP, DGRD, TXD1/2, RXD1/2, DI, EI, XYFS, CVXTY, CVYTX, PULS1/2/3, PWM1/2/3, RAMP1/2, ZRN1/2/3, PID, DTML, DTIM,
DTMH, DTMS, TTIM, RUNA, and STPA.
For wiring the interrupt input signals, use a twisted-pair shielded cable.
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