Test: Instruction Sets & Data Formats - Electronics and Communication Engineering (ECE) MCQ

Number of T-states in each machine cycle = 3 So, number of T-states in 4 machine cycles = 3 x 4 = 12

Given, f = 3 MHz

Thus, time required for execution of the instruction

• Instruction ‘CMP C’ compares the contents of register C with the content of accumulator A but contents of A and C will remain unchanged.
• Instruction ‘CPI 3A H' compares the 8-bit data 3A H with the contents of accumulator A but contents of A and C will remain unchanged.
• In instruction ‘AN! 5C H’, the 8-bit data 5C H is ANDed with contents of A and result is stored in A. So, the content of accumulator changes.
• In instruction ‘ORA A’, contents of A are ORed with contents of A itself and result is stored in A. But, the result of operation remains same as contents before execution ' of ORA A.

Hence, the contents of A does not change.

In immediate addressing mode, an 8 bit or 16 bit data Is given In the instruction as operand.

Initially contents of accumulator A = AA H.
The instruction CPI 99 H compares the data 99H w ith the content of accumulator (A). This comparison is made by subtracting 99 H from contents of A i.e. AA H.
The contents of accumulator will remain unaffected but status of result will be reflected by flags

Hence, after comparison both carry and zero flags will be reset

Decrement the content of B by one (initially B = 00 H)

B= FF H

D A A ; D A A instruction changes the binary values of contents of accumulator to BCD.
Since lower order nibble of A is more than 9 (i.e. C), AC flag is set and upper nibble is less than 9, therefore DAA adds 0110 H to lower order nibble of A to adjust binary result to Binary coded decimal.

2040 HLT ; Halts the execution of program Hence, the content of accumulator after the execution of given program are 40 H.

PUSH D stores the content of register pair DE on two top locations of stack, it is a 1 byte instruction and uses register indirect addressing mode.

An instruction cycle is the time in which, a hardwired controller completes the following four functions;
(i) fetching of code from memory
(ii) updating the program counter
(iii) decoding of the instruction code
(iv) execution of the instruction

CALL and RET instruction uses stack while JMP instruction does not uses stack.