Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Multiplexing

Status
Not open for further replies.

didimus

New Member
Hello guys!

This question is because of reduced number of interrupts on a micro. I have 3 signals that are low active and only one interrupt. I need to be able to sense every lowering edge of the signals. If I use a nand gate, I will have a problem sensing a second lowering edge because the nand gate output is already set by the first lowering edge. I could use a regular port (GPIO), put I wanna avoid sweeping on the code.

Is there a hardware that could help me interface the signals?

Any sugestion? Anyone?

Thanks in advance.
 

RCinFLA

Well-Known Member
I assume you mean you have three inputs that trigger a common single interrupt when any of the three ports goes low.

I also assume you have checked the particular processor to see if it has a configuration for the interrupts.

How do you plan on inputting the three separate interrupts assuming you externally generate them? If you want to avoid scanning code you will need three other interrupt generating ports on the micro, in which case you probably don't need an external hardware solution.

Upon reading port, immediately clear interrupt so it is ready to catch another. Some micros clear interrupt automatically on port read. You will be vunerable only for the few micro clock cycles between the two instructions. Better then this requires three independent interrupt ports.
 
Last edited:

Mikebits

Well-Known Member
In the old days they would use a Priority Interrupt Controller A priority interrupt controller like the 8259. I think you could also do this in SW on your cpu chip of choice, but this will depend on your needed poll rate.
Check this link.

Priority Interrupt Controller
 
Last edited:

kchriste

New Member
Forum Supporter
This question is because of reduced number of interrupts on a micro.
Some micros have interrupt on change for an entire 8bit port. What micro are you using?
 

sanalece

New Member
This Idea May Help you

Picture1.jpg

Picture1.jpg




The Above logic is a simple idea, But you can use this...!


But if you want to know the interrupt from which line then it will not help you.. For entire Interrupt if you have same ISR, then you can ........!

If you need more write in...
 
Last edited:

Mikebits

Well-Known Member
The usual interrupt is a way for a peripheral device to signal the mcu, saying, yo I need some service here. Now anding all IRQ's to one line would create a situation for the mcu, which device is requesting service? I suppose any interrupt generated could initiate a service to all 3 peripheral devices, but this would be a misuse of efficiency and speed. Again, if you can sacrifice the service of all 3 devices per IRQ then I suppose it is no big deal.
 
Last edited:
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top