F28379D: one part of the code behaves differently in External mode
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I am testing a bespoke control code on TI ControlCard F28379D and working on a protection part. It seems one part of the code behaves differently when I am running the application in External mode.
I am sending a measured signal and limit to SR flip flop. If the value is higher than the limit, I should latch the error and block pulses. The same code is used for current and voltage, as shown in the figure. To test, I am sending signals to digital outputs and recording them on the oscilloscope.
On the scope, the first SR flip-flop output is oscillating (GPIO 67, PIN 132, Ch4), although both inputs are zero (LOW) (GPIO 36 and GPIO 35 (Reset), Ch1 and Ch2). For the second SR flip-flop inputs are also zero (LOW) and the output is zero (LOW), as it should be. I have not uploaded that case.
Oscillation is 2.5kHz. My sample time is 5kHz.
When not in External mode, there is no oscillation and the SR logic works ok, i.e. as expected.
Is there any explanation behind it and what can I do to fix it?