1. BRX Technical Training
Interrupts

2. Interrupts BX10 BX10E 6 discrete IN (all high-speed)
4 discrete OUT (2 high-speed)
No analog IN
No analog OUT
No Ethernet port
BX10E
1 analog IN
1 analog OUT
Ethernet port

3. Interrupts BX18 BX18E 10 discrete IN (all high-speed)
8 discrete OUT (4 high-speed)
No analog IN
No analog OUT
No Ethernet port
BX18E
1 analog IN
1 analog OUT
Ethernet port

4. Interrupts BX36 BX36E 20 discrete IN (10 high-speed)
16 discrete OUT (8 high-speed)
No analog IN
No analog OUT
No Ethernet port
BX36E
4 analog IN
2 analog OUT
Ethernet port

5. Interrupts (Why?) Inputs are normally read at top of scan
Outputs are normally written to at bottom of scan
If input changes during scan, it is not seen by logic until the next scan
Most of the time this is OK because scan times are so fast for industrial world
Interrupts allow an input to be seen during scan
Interrupts allow an output to be changed during scan
3 types of triggers for generating interrupts:
Events (up to 4)
Timers (up to 4)
Match registers (up to 4)
Each interrupt calls an ISR
Only on-board inputs can be used
Doesn’t have to be high-speed inputs
Read Inputs
Code Blocks
Write Outputs

6. Interrupts (Input Events)
Uses onboard input(s) to trigger interrupt
Expansion I/O cannot be used
Input Event:
Prequalifiers
Levels
High
Low
None or up to 19
Levels are AND’d (i.e. all have to be true)
Event
Edges
Rising
Falling
Either
1 or up to 20
Edges are OR’d (i.e. any one will trigger interrupt)
Name of ISR that is called
LEVELS (all must be true):
If X13 is LOW
AND X14 is HIGH
AND X15 is HIGH
AND X19 is HIGH
…THEN…
Read as:
MyISR gets invoked if X13 is low (!X13) and X14 is high AND X15 is high and X19 is high and then either a rising edge is seen on X0 (pX0), or a falling edge on X1 (nX1) or either edge on X2 (nX2 | pX2)
If all LEVELS are true then…
EDGES (any is true)
If there’s a rising edge on X0
OR there’s a falling edge on X1
OR there’s any edge on X2
… THEN…
Call MyISR

7. Interrupts (Timer) Uses hardware 1µsec timer Timer Mode Timer Duration
Recurrent
One Shot
Timer Duration
1 to 2,147,483,647 µsec (35 min, sec)
Name of ISR that is called

8. Interrupts (Timer Example)
Test example to compare between 4 ways of doing a 1-second timer that toggles an output
Each method will utilize Tickus() function in MATH to calculate the ON time of the toggle
TMR Instruction to toggle Y0
D1 = current measured time in µsec
D2 = current difference from 1 second
D3 = maximum difference from 1 second
ENTASK instruction to toggle Y1
D5 = current measured time in µsec
D6 = current difference from 1 second
D7 = maximum difference from 1 second
t$1Second to toggle Y2
D9 = current measured time in µsec
D10 = current difference from 1 second
D11 = maximum difference from 1 second
Interrupt Timer to toggle Y3
D13 = current measured time in µsec
D14 = current difference from 1 second
D15 = maximum difference from 1 second

9. Interrupts (Timer Example)
1-sec TMR Instruction = $Main
T0 resets itself
Calculate the difference from 1 second (1,000,000 µsec), store in D2
PONOFF toggles Y0 every 1 second
When Y0 comes ON store TICKus() in D0
When Y0 goes OFF store difference between TICKus() in D0 into D1
Store the maximum difference into D3

10. Interrupts (Timer Example)
ENTASK (enables Toggle_Y1)

11. Interrupts (Timer Example)
Toggle_Y1 Task

12. Interrupts (Timer Example)
$t1Second

13. Interrupts (Timer Example)
Configuration
Recurrent Timer with a duration of 1 second (1,000,000 µsec) that executes Toggle_Y3 ISR

14. Interrupts (Timer Example)
ISR Toggle_Y3

15. Interrupts (Timer Example)
Typical Accuracy
TMR varies by 583µsec
User Task varies by 579µsec
$t1Second varies by 578µsec
Timed Interrupt varies only 2µsec!

16. Interrupts (Timer Example)
D14 gray line’s standard deviation is negligible

17. Interrupts (Match Registers)
Monitors high-speed I/O register values
Ctr/Tmr Accumulator (1, 2, 3)
Pulse Output Position (1, 2, 3)
Comparison
=, !=, >, >=, <, <=
…to an integer value (signed double-word)
Name of ISR that is called

18. Interrupts (Match Registers Example)
Will compare the ability of ladder logic comparative contact VS Match Register interrupt, to see a specific (=; equal to) value in a high-speed position count
Axis1 = virtual axis
D0 = random new position (0 to 1,500,000)
1,000,000 = position in which to toggle output
Y6 = output for Match Register Interrupt to toggle
Y7 = output for ladder logic comparative contact to toggle

19. Interrupts (Match Registers Example)
Configuration

20. Interrupts (Match Registers Example)
$Main
Ladder comparative
Configures Axis1 as a virtual axis
Calculate a random new position
Move to the new position which might cross position 1,000,000

21. Interrupts (Match Registers Example)
ISR = MyMatch
Toggles Y6 immediately

22. Interrupts (Match Registers Example)
Position 1,000,000 in Green
Typical Results
Ladder logic Y7 never toggles
Match Register Interrupt always happens when current position exactly equals 1,000,000
Ladder logic compare never happens

23. Interrupts (Instructions)
INTSUSPEND “Suspend Interrupts”
Edge triggered – suspend interrupts when input leg goes from OFF to ON
Power flow enabled – suspend interrupts while the input leg is ON
INTRESUME “Resume Interrupts”
Clear any Pending interrupts
If multiple interrupts occur during suspension, they “want” to run after resumption & will run in priority order; this selection makes sure they don’t run at all
Edge triggered
Power flow enabled
Code Blocks
No Interrupts

24. Interrupts (Instructions)
INTCONFIG “Configure Interrupt”
Allows interrupts to be configured just like the System Configuration dialog
3 tabs for configuring (Input Event, Timer, Match Register)
Edge triggered or Power flow enabled
Can use <Load from System Config> button to pull data in from what is already configured there
Can use variables in the instruction whereas variables cannot be used in the System Configuration

25. Interrupts (INTCONFIG Example)
Will generate a pulse with a 3-second period but with a variable duty cycle:
D0 = Duty Cycle in percent
D1 = ON time of pulse
D2 = OFF time of pulse

26. Interrupts (INTCONFIG Example)
Configuration & the ISR (MyPulse)
D0 = DutyCycle (in percent)
Based on Duty Cycle (D0) ON & OFF times are calculated
When Y6 is OFF reconfigure Timer interrupt for ON time
When Y6 is ON reconfigure Timer interrupt for OFF time
Timer Interrupt configuration just kicks things off 2 seconds (2,000,000 µsec) after Program-to-Run transition
Toggle Y6 immediately

27. Interrupts (INTCONFIG Example)
Results
D0 = DutyCycle
10% Duty Cycle (D0)
3-second period
ON time = 0.3 sec
OFF time = 2.7 sec