Match List - I with List - II. Choose the correct answer from the options given below :List - I (8086 Instruction) List - II (Addressing mode) (A) MOV BX, AX (I) Register Relative Addressing (B) MOV AX, 50H[BX] (II) Direct Addressing (C) MOV AX, [BX] (III) Register addressing (D) MOV AX, [2000H] (IV) Register Indirect Addressing
(A)-(III), (B)-(I), (C)-(IV), (D)-(II)
The addressing mode is read off the syntax of the source operand — brackets and displacements are the tell. The code is (A)-(III), (B)-(I), (C)-(IV), (D)-(II), option 3.
| Instruction | Source operand | Mode | Where the data is |
|---|---|---|---|
| MOV BX, AX | A register, no brackets | Register | In AX itself |
| MOV AX, 50H[BX] | Displacement + bracketed register | Register relative | At address BX + 50H |
| MOV AX, [BX] | Bracketed register alone | Register indirect | At the address held in BX |
| MOV AX, [2000H] | Bracketed constant | Direct | At address 2000H |
The brackets are the key. Without them the operand is the data; with them the operand is the address of the data. So MOV BX, AX copies a value, while MOV AX, [BX] uses BX as a pointer — the same register, two entirely different meanings.
Distinguishing (B) from (C). Both use BX as a pointer, but (B) adds a fixed displacement of 50H to it. That makes it register relative, and it is exactly how a field within a record or an element of an array is reached: BX holds the base of the structure and the displacement selects the member. Effective address arithmetic in the 8086 is
\(EA=\text{base}+\text{index}+\text{displacement}\)
with register indirect using only the first term, register relative the first and third, and base-plus-index all three.
Distinguishing (A) from (D) is the other easy pair: (A) has no brackets at all, so no memory is touched and the instruction is the fastest kind — register to register. (D) has brackets round a constant, so the address is fixed at assembly time and cannot be changed while the program runs, which is what makes it direct rather than indirect.
Why the distinction matters practically. Only the indirect and relative forms allow a loop to walk through data, since only they compute the address at run time from a register that can be incremented. Direct addressing is faster for a single fixed variable but useless for arrays.
Hence, the correct code is (A)-(III), (B)-(I), (C)-(IV), (D)-(II).
Similar Questions
$D_7$ $D_6$ $D_5$ $D_4$ $D_3$ $D_2$ $D_1$ $D_0$ In 8255 programmable peripheral interface device, if the port A and port B are to be set in a hand shake mode along with port C, what are the bits in the 8 bit control word to be set as 0 1 0.
The number system for the machine code of the microprocessor 8085 is
Which of the options in a multipurpose instruction used to implement the interrupt of 8085 and serial data input ?
Both 8155 and 8255 programmable peripheral interface ICs have the following common features :
(i) Programmable I/Os
(ii) Either port A or Port B can be set as either input or output ports.
(iii) One 14-bit down counter
(iv) AD0 – AD7 are multiplexed address/datalines.Each instruction in an assembly program has the following fields :
(i) Lable field
(ii) Operand field
(iii) Comment field
(iv) Mnemonic fieldPlease write the proper sequence of fields :
The mnemonic of 8085 processor indicate :
List – I List – II a. RLC i. Rotate Accumulator Right through carry b. RRC ii. Rotate Accumulator Left through carry c. RAR iii. Rotate Accumulator Left d. RAL iv. Rotate Accumulator Right Codes :
Match the following :
List – I (Pin terminals) List – II (Applications) a. SID, SOD i. Wait state b. READY ii. Serial data transfer c. TRAP iii. Address Latch Control d. ALE iv. Interrupt Codes :
Assertion (A) : In serial communication system, when the transmission of data goes in both ways, it is called full-duplex system. Now if two micro processors are connected in full duplex mode, the amount of data transmitted will be double to the amount of data in half-duplex mode connection.
Reason (R) : When the transmission of data goes in one way, it is called half-duplex system and when the data moves in both ways, it is called full duplex system.
The assembler directive used to give name to some value or symbol for 8086 ASM-86 is
Which of the following peripherals provide I/O facilities ?
i. 8279
ii. 8155
iii. 8259
iv. 8255
Important Questions from Microprocessors
An 8086 address bus is a/an _____ -bit bus
Match the columns.
Pin
Description
a. D 0-D 7
1. Reset Input
b. RESET
2. Data Lines
c. A 0,A 1
3. Internal Address
An 8 bit microcontroller has an external RAM with the memory map from 8000 H to 9FFF H. How many number of bytes can this RAM store?
In 8085 microprocessor, initially the number decimal 8 is stored. If instruction RAL is executed twice on this number, the final number stored will be
Which of the following 8085 microprocessor instructions occupies 3 bytes in memory?
