Hello guys, can I monitor interrupt0 of 8051 by any h/w means like by LED or something? I have connected RTC DS12887 IRQ to INT0 however I couldn't see logic 1 on DMM
Hello guys, can I monitor interrupt0 of 8051 by any h/w means like by LED or something?<p>
Well, if you're measuring with a multimeter, you're already trying to monitor by h/w means. If a multimeter can correctly resolve fast transients like IRQ signals is another question - the usual way of monitoring signals like this would be using an oscilloscope if available.
A LED could be used, too, depending on how long the interrupt line stays active/inactive. A current-limiting resistor might be necessary.
Thanks Franck Here is what I think - 1. Interrupts are just transient changes 2. And AT89C51 requires active low interrupts i.e. 0V - logic 0 So I hope whenever I connect DMM on link between DS12887 IRQ and INT0, I should see high voltage logic1 but I however I can see is 0V
but I however I can see is 0V
I'm not all that familiar with that particular RTC device, but could it be that it is already signaling an interrupt and waiting for it to be serviced ?
no actually RTC gives interrupt only when current time matches with predefined/alarm time and I'm checking the voltage at the system start up still i can get is 0V and i double checked it. anyway the zero on IRQ of RTC stays only for short amount of time(transient)
The interrupt output is open-drain, i.e. it will basically tristate when not signaling an interrupt. Have you remembered to connect a pull-up resistor?
no actually RTC gives interrupt only when current time matches with predefined/alarm time
Ok, I've dug out the data sheet for the part, and if I understand it correctly, this statement is not correct. The part has three different interrupt sources that can all lead to IRQ being set to low (active).
anyway the zero on IRQ of RTC stays only for short amount of time(transient)
That is also incorrect, according to the data sheet IRQ stays low until the control register C is read.
Oh, and make sure that the 8051 isn't pulling the port pin to low (i.e. don't set the latch for the pin to 0).
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