← All revision guidesSEMESTER 4 · DI04000171
6FLASHCARDSMicrocontroller Applications
8051 architecture, programming, timers and hardware interfacing.
8051 fundamentals
Q1What is the function of the program counter?
It holds the address of the next instruction to be fetched from program memory.
Q2Why are ports P0 and P2 used during external-memory access?
P0 carries the multiplexed low-order address and data bus, while P2 carries the high-order address bus.
Q3What does the stack pointer contain?
It contains the internal RAM address of the current top of the stack.
Timers and interfacing
Q1How is a timer different from a counter in the 8051?
A timer counts internal machine-cycle pulses; a counter counts external transitions on its input pin.
Q2Why is a flyback diode connected across a relay coil?
It provides a path for coil current when switching off and limits the damaging inductive voltage spike.
Q3What is switch debouncing?
It removes the rapid false transitions produced by mechanical contact bounce, using hardware or a timed software check.