Rockwell Automation 57C419 5V-24V DC Input Module - Manual (Page 23)

4Ć7
4.4.2 Control Block Task Example
The following is an example of a Control Block task that handles an
interrupt from input B19.
Note that the `timeout' parameter in the BASIC statement EVENT is
usually disabled since interrupts from this module do not generally
ocur on a timed basis. The same consideration requires care in using
timeĆbased statements in loops used to read inputs from the module.
The `timeout' parameter is not disabled in the following example
because the interrupt is expected to happen in a specified time
period.
1000 COMMON ISCR% \!Interrupt Status/Control Register
1010 COMMON LATCH EDGE B19@ \!Latch edge, input B19
1020 COMMON LATCH STATUS B19@ \!Latch status, input B19
1030 COMMON LATCH ENABLE B19@ \!Interrupt enable, input B19
1040 COMMON LATCH RESET B19@ \!Latch reset, input B19
1050 LOCAL B19 CNT% \!Count of interrupts
2000 !
2001 ! Define the edge transition that will generate an interrupt.
2002 !
2010 LATCH EDGE B19@ = FALSE \!Off to on
3000 !
3001 ! The following statement connects the name HW EVENT to the
3002 ! Interrupt defined in ISCR%. The event name should be
3003 ! as meaningful as possible. The watchdog timeout has been
3004 ! set to 1800 clock ticks (9.9 sec.). 1 tick equals
3005 ! .0055 seconds. If the time between
3006 ! interrupts exceeds this value, a severe error will be declared
3007 ! and the system will be stopped.
3008 !
3009 !
3010 EVENT NAME=HW EVENT, LATCH STATUS=ISCR%, & TIMEOUT=1800
4000 !
4001 ! The following statement resets the latch status bit
4002 !
4010 LATCH RESET B19@ = FALSE
5000 !
5001 ! The following statement enables interrupts
5002 !
5010 INTRP ENABLE B19@ = TRUE
5200 !
5300 ! complete the remainder of task initilization
5500 !
6000 !
6001 ! The next statement synchronizes the task with the external
6002 ! event via the interrupt. Task execution will be suspended
6003 ! until the interrupt occurs. When the interrupt occurs, if this
6004 ! task is the highest priority task waiting to execute, it will
6005 ! become active. If it is not the highest priority task, it will
6006 ! remain suspended until all higher priority tasks have executed.
6007 ! at which point it will become active.
6008 !
6010 CALL SCAN LOOP( TICKS=1200, EVENT=HW EVENT)
7000 !
7001 ! The next statements determine which bit generated the interrupt
7002 ! by examining the latch status bit. If an interrupt is
7003 ! found, it is reset. The interrupt service routine is
7004 ! then executed.
7005 !
7500 !