Priority AND GateThe Priority AND (PAND) gate is used to indicate that the output occurs if and only if all input events occur in a particular order. The order is the same as that in which the inputs events are connected to the PAND gate from left to right. The PAND gate is a dynamic gate, which means that the order of the occurrence of input events is important to determining the output.
The output of a PAND gate can be the top event or an intermediate event. The inputs can be basic events or outputs of any AND gate, OR gate, or dynamic gate, which includes the SPARE gate, PAND gate, sequence-enforcing (SEQ) gate and functional dependency (FDEP) gate. (These gates should have the inputs from basic events or other AND gates and OR gates.) The items that enter a PAND gate need to fail in temporal order from left to right to trigger the event. The PAND gate also supports a single input. When only a single input exists, then occurrence of that input will trigger the event.
Logic Summary
All input events must be true (T) for the output to be true (T) and the events must occur from left to right in the temporal order. Table 5-9 shows the input and output events for a PAND gate.
Input A | Input B | Output |
|---|---|---|
T(1) | T(2) | T |
T(2) | F(1) | F |
T | F | F |
F | T | F |
F | F | F |