3 timer and latch mode example – Rockwell Automation 57C421B Pulsetach Input Module/DCS 5000/AutoMax User Manual

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4.4.3

Timer and Latch Mode Example

The following is an example of a BASIC task that handles interrupts

from the module. All variables declared as COMMON are assumed

to have previously been defined during configuration.
In the example below, the task counts pulses generated by the

internal 200 kHz clock. Each time an external latch input signal is

received, the task latches the counter data and then clears the

counter.

!ă

!ăTIMER AND EXTERNAL LATCH MODE EXAMPLE

!ăTASK NAME: PG_LATCH

!ăPRIORITY: 10

!ă

1000

COMMON COUNT%

\!ăCounter data

1005

COMMON ISCR%

\!ăInterrupt status & control

1010

COMMON RESET@

\!ăCounter reset

1015

COMMON EXT_LATCH_EN@ \!ăExternal latch enable

1020

COMMON LATCH_POLARITY@ \!ăExternal latch polarity

1025

COMMON LATCH_RESET@

\!ăExternal latch interrupt reset

1030

COMMON TIM_MOD@

1035

COMMON LAT_INT@

1040

COMMON CCLK_EN@

1045

COMMON CLR_MOD1@

1050

COMMON CLR_MOD2@

1200

LOCAL DELTA%

\!ăTime between external events

3000

!ă

3001

!ăThe following statement connects the name COUNTER_EVENT

3002

!ăto the interrupt defined in ISCR%. The event name should

3003

!ăbe as descriptive as possible. The watchdog timeout has

3004

!ăbeen disabled because the event is not periodic.

3005

!ă

3006

!ă

3007

!ă

3010

EVENT NAME=COUNTER_EVENT, INTERRUPT_STATUS=ISCR% ă

ă&

TIMEOUT=DISABLED

4000

4001

!ăThe following statements initialize the counter and set

4002

!ăup the interrupt control. Constant clock" is enabled on

4003

!ăthis module. If there is more than one interrupt task in

4004

!ăa chassis, the task that enables constant clock" should

4005

!ăalways be the lowest priority task.

4006

!ă

4010

RESET@ = TRUE \ RESET@ = FALSE \!ăZero counter

4015

EXT_LATCH_EN@ = TRUE

\!ăEnable the external latch

4020

LATCH_POLARITY@ = FALSE \!ăLatch input is high true

4025

TIM_MOD@ = ON

\! Timer mode

4030

LAT_INT@ = ON

\! External latch int. enable

4035

CLR_MOD1@ = OFF

\! Clear counter after

4040

CLR_MOD2@ = ON

\! External latch

4045

CCLK_EN@ = ON

\! Enable CCLK

5988

5989

!ăPlace additional initialization software here.

5990

5991

!ă

5992

!ăThe next statement synchronizes the task to the occurence

5993

!ăof the external latch via the interrupt. Task execution

5994

!ăwill be suspended until the interrupt occurs. When the

5995

!ăinterrupt occurs, if this task is the highest priority

5996

!ătask waiting to execute, it will become active. If it is

5997

!ănot the highest priority task, it will remain suspended

5998

!ăuntil all other higher priority tasks have been executed

5999

!ăat which point it will then become active.

6000

WAIT ON COUNTER_EVENT

6997

6998

!ăThe following statements perform the interrupt service

6999

!ăroutine.

7000

DELTA% = COUNT%

\!ăRead time between external events

7005

LATCH_RESET@ = FALSE

\!ăReset the interrupt

7010

GOTO 6000

\!ăWait for the next event

32767

END