Test: I/O Port Programming And Addressing Modes - Computer Science Engineering (CSE) MCQ

In 8051, a port is initialised by default in its output mode no need to pass any value to it.

These pins are the open drain pins of the controller which means it needs a pull-up resistor for using it as an input or an output ports.

 PORT 0 and PORT 2 are used as the 16 bit address lines where PORT0 act as lower bit address lines and PORT 2 as higher bit address lines.

 PCON register is not a bit addressable register.

JNB which stands for Jump if no bit checks the status of the bit P0.0 and jumps if the bit is 0.

 If we want to push or pop any element on or from the stack then direct addressing mode has to be used in it, as the other way is not accepted.

 In register indirect mode data is copied at that location where R0 or R1 are present, so @ operator is used ex. MOV @R0,A

Register indirect addressing mode is useful if a series of data is to be assigned to that address, with the help of this quality the number of instructions decreases as a result of which performance increases.

 Indexed addressing mode stand for that instruction where the bits of accumulator are also indexed with the 16 bit registers.

SETB is used to set a bit of a register. A stands for accumulator which is an 8 bit register, so it is an invalid instruction.