Do I need a hardware interrupt in S7?

Hi all,

I'm currently upgrading an S5 system to S7 and I'm trying to recreate the functionality.

The S5 system has a 434 card on it which is basically a card that calls an interrupt OB (OB 2) every time one of the 8 inputs goes high.

The interrupt OB 2 then checks which input went high and either adds 1 to a count or subtracts 1 from a count. It does this for a vertical and a horizontal axis.

The machine has two toothed sprockets and proxy sensors counting the pulses.

I need to recreate this functionality in my S7. I'm using an S7-314C-2DP as this is quite a quick PLC.

I can set up that the pulses from the proxys come into the High Speed Counter that's built into the 314C-2DP.

My question is this..

Do I need to set up an interrupt like they have done in S5? If so, how would I go about it. I've looked into the OB's in S7 and there's OB30 - OB38 which are Cyclic Interrupts. There's also OB40 - OB47 which are "hardware interrupts".

I'm guessing that its the hardware interrupt I need but I've never had any dealings with them whatsoever so I'm a bit stuck.

Can someone tell me how to set up a hardware interrupt or has anyone got any better ideas on how I can achieve the same thing another way??

A really big thank you to anyone who can help me out with this. I must have downloaded and searched through about ten manuals from the Siemens site and I'm getting nowhere!

Cheers

To find if you need interrupts compare lenght of pulses with your longest programm scan time (OB1) - if pulses are shorter then you need them for sure.
In case of your CPU you can use HW interrupts with on-board binary inputs. It can be enabled in HW Config when you double click slot 2.2 of your CPU. I believe configuration is straightforward.
Then you add OB40 to your Blocks folder. Every time interrupt comes, OB40 is started. Here you can programm your logic.
(however observe manual what happens if next interrupt emerges while previous one is still being processed).
You can check which input fired the interrupt in OB startup variable: OB40_POINT_ADDR

Thanks for the information on the hardware interrupts. I've searched the hardware config and found them as you said. I've also managed to set them up now.

I'm wondering if I need them..

My scan time says it is 11ms (between 10 and 12ms)

I need to count roughly 1000 pulses in 9 seconds.

This is a pulse every 9ms

My questions are...

1) Do you think I'd get away without a hardware interrupt or is the hw interrupt the way to go??

2) Would I really need to implement the built in high speed "counter" if I'm using hardware interrupts. I'm not bothered about the actual count just making sure that I 'see' all the pulses so that I can internally compare the position to a set position and stop the motor in the right place.

Many thanks for your help

Use the h/w interrupt.

To supplement L D[AR2,P#0.0] answer - no need for HSC - you can program your counting in OB40 as you like.

Brilliant...

A big thanks for clearing that up for me.

Cheers