BINARYUPDATES.COM EMBEDDED SYSTEMS TRAINING
What is PSW? Give Its Structure?
The current state of processor is stored in a register called Processor Status Word (PSW). The PSW contains bits which indicate such things as whether the previous arithmetic operation produced a positive, negative or zero result. If a subtract instruction is followed by a “branch on zero” instruction then the branch will be taken if the PSW indicates that the subtraction resulted in a zero. Most loop such as DO-WHILE, FOR etc. involve incrementing or decrementing counter and repeating the loop until the counter reaches the limit. Each time the counter is changed, the result is compared with the limit. The PSW is set accordingly and branch is taken or not depending on the content of PSW. The 8086 microprocessor has 16-bit PSW.
What is difference between JMP and CALL Instruction?
A JMP instruction permanently changes the program counter. A CALL instruction leaves information on stack so that the original program execution sequence can be resumed.
Explain CALL and RETURN?
It calls 16-bit memory address of a subroutine. It is a 3-byte instruction that transfers the program sequence to a subroutine saves the content of the PC (Program Counter 16-bit register), the address of the next instruction on the stack decrements the stack pointer register by 2. Jumps unconditionally to the memory location specified by the 2nd and 3rd bytes. This instruction is accompanied by a return instruction in the subroutine. The return instruction is used either to return a function value or to terminate the execution of a function. The exit maybe from anywhere within the function body including loops or nested blocks. If the function returns a value, the return instruction in required.
What is the use of HLDA?
HLDA is the acknowledge signal for HOLD. It indicates whether the HOLD signal is received or not. HOLD and HLDA are used as the control signal for DMA operation.
What is the role of READY Pin?
READY is used by microprocessor to check whether a peripheral is ready to accept or transfer data. If READY pin is high then the peripheral is ready for data transfer. If not then microprocessor wait until READY goes High.
What is difference between instructions MUL and IMUL?
MUL: instruction is used for unsigned multiplication. This instruction multiplies bytes or words. IMUL: (Integer Multiply) Instruction is used for signed multiplication.
[adToAppearHere1]What are the flags available in 8086?- Control Flags: Direction, Interrupt, Trap
- Condition Flags: CY, AC, S, Z, P, OV
What are special registers available in 8086?
IP, CS, DS, SS, ES
What is SIM and RIM Instruction?
SIM: (Set Interrupt Mask) used to mask the hardware interrupt. RIM: (Read Interrupt Mask) used to check whether the interrupt is masked or not.
What is difference between SHIFT and ROTATE Instruction?
- SHIFT and ROTATE commands are used to convert a number to another form where some bits are shifted or rotated.
- A rotate instruction is closed loop instruction. That is the data moved out at one end is put back in at the other end.
- The shift instruction loses the data that is moved out of the last bit locations.
- Basic difference between shift and rotate is shift command makes “fall of” bits at the end of the register. Where rotate command makes “wrap around” at the end of the register.
