Write down the functions of control flags in flag register.

Control Flags: The control flags enable or disable certain operations of the microprocessor. There are 3 control flags in 8086 microprocessor and these are:

(i) Directional Flag (D): This flag is specifically used in string instructions. If directional flag is set (1), then access the string data from higher memory location towards lower memory location. If directional flag is reset (0), then access the string data from lower memory location towards higher memory location.

(ii) Interrupt Flag (I): This flag is for interrupts. If interrupt flag is set (1), the microprocessor will recognize interrupt requests from the peripherals. If interrupt flag is reset (0), the microprocessor will not recognize any interrupt requests and will ignore them.

(iii) Trap Flag (T): This flag is used for on chip debugging. Setting trap flag puts the microprocessor into single step mode for debugging. In single stepping, the microprocessor executes a instruction and enters into single step ISR if trap flag is set (1), the CPU automatically generates an internal interrupt after each instruction, allowing a program to be inspected as it executes instruction by instruction.

If trap flag is reset (0), no function is performed.