Interrupts (BRK / NMI / IRQ) implicitly push P to the stack. Interrupts returning with RTI will implicitly pull P from the stack.
The effect of toggling the IF flag is delayed by 1 instruction when caused by SEI, CLI, or PLP.
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| S (Stack Pointer) || 8-bit || Points to the current location in the stack || Stack is located in page 1 ($0100-$01FF), 8-bit S register is offset to this base