Microprocessors - Question and Answer - 1

1. Explain briefly what happened when the INTR signal goes High in 8085 ?
The INTR is lowest priority, non-vectored and masks able interrupt for 8085. This INTR signal goes into a High state in many instances, whenever this condition occurs following things occur. For every step in the set of instruction that happens the 8085 checks the status of INTR interrupt, if it has occurred. Until completion of every step, the status of the INTR signal remains High. As soon as this instruction is completed, the processor sends the completion signal to INTR. As INTR signal receives this completion signal, a new operation code is placed on a data bus to transfer it for execution. The processor receives this new operation code address, saves this address on STACK and new interrupt service subroutine begins.

2. Explain brief on SIM and RIM instructions ?
The RIM instruction means Read Interrupt Mask which is used to read the status of interrupts which are pending or yet to be executed and SIM means Set Interrupt Mask which is used to set those interrupts. In both the cases the operation is done through the accumulator only. Here's and insight to the process. SIM is Set Interrupt Mask. Used to mask the hardware interrupts. RIM is Read Interrupt Mask. Used to check whether the interrupt is Masked or not.

3. What are the flags in 8086 ?
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.

4. What are the 3 control flags in 8086 microprocessor ?
Directional Flag (D) - This flag is specifically used in string instructions.
Interrupt Flag (I) - This flag is for interrupts.
Trap Flag (T) - This flag is used for on-chip debugging.

5. What are the different functional units in 8086 ?
EU (Execution Unit) and BIU (Bus Interface Unit).

1 2 3 4 5 6 7 8 9 10