An example of moore model circuit is shown in the below diagram. In this circuit, two JK flip flops are connected together. The input is connected only to the first JK flip flop.
The output is the multiplication of the next state output, but not of the input. The output depends on the present state of the flip flops and the input. The circuit shown below is an example of Mealy circuit model. As you can see, the output is the product of the present state of flip flop and the input.
The change in input signals can affect the memory element at any instant of time. The memory units do not have clock pulses. Instead, they have time delay elements. A clock pulse is a continuously changing signal that oscillates between a high state and a low state. A clock pulse is shown below. While applying the clock pulse to the flip flop, it gets triggered by two ways, Level triggering and edge triggering. In this, the flip flop is triggered only during the high-level or the low level of the clock pulse.
In a sequential circuit , the output changes depending on the triggering. There are two types of triggering as edge and level triggering. There are two levels in a clock pulse or a signal. One is a high voltage V H , and the other is low voltage V L. Furthermore, these voltage levels help to determine the triggering type. What is Edge Triggering — Definition, Functionality 2.
What is Level Triggering — Definition, Functionality 3. In a sequential circuit, if the output changes when the signal transits from a high level to a low level or from a low level to a high level, we call it edge triggering.
Here, the edge that changes the voltage from low level to the high level is called rising edge positive edge. And, the edge that changes the voltage from high level to the low level is called falling edge negative edge. Thus, when an event is triggered at the rising edge or falling edge, we call it edge triggering. On an , TRAP is a non-maskable interrupt normally used to handle errors such as a power failure. If it were level triggered, its code could never execute because it's an unmaskable interrupt.
The handler would start executing when it became active, but it would still be active, so the handler would start executing, but it would still be active, so the handler would start executing, etc. Therefore it has to be edge triggered. However, edge triggering is a problem when the line may have glitches. Glitches may cause the handler to be invoked multiple time as the line glitches. As a compromise, the TRAP works as if it is level triggered, except that it is only recognized when it has been low since the last time it was recognized.
That ensures that the TRAP handler is only invoked once. In level triggering the circuit will become active when the gating or clock pulse is on a particular level. In edge triggering the circuit becomes active at negative or positive edge of the clock signal. In short, edge interrupt gets fired only on changing edges, while level interrupts gets fired as long as the pulse is low or high.
My impression is that no one has really answered what it means to be both level- and edge- triggered. And I haven't, either. D Krueger's answer correctly explains what it means to be both level- and edge- triggered. At least, his answer sounds correct to me, even though I'm not familiar with the Golaz and vsz's answer assumes that the interrupt is masked.
I'm still not sure how "except that it is only recognized when it has been low since the last time it was recognized.
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