The mnemonic of 8085 processor indicate : Codes :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
a-iii, b-iv, c-i, d-ii
The rule that decodes all four mnemonics: the letter C at the end means the rotation is within the accumulator, while the letter A in the middle means the carry is included in the loop.
| Mnemonic | Meaning | Match |
|---|---|---|
| RLC | Rotate accumulator Left, 8-bit | iii |
| RRC | Rotate accumulator Right, 8-bit | iv |
| RAR | Rotate Accumulator Right through carry, 9-bit | i |
| RAL | Rotate Accumulator Left through carry, 9-bit | ii |
So a-iii, b-iv, c-i, d-ii — option 1.
What each instruction actually does. RLC shifts every bit one place left and wraps D7 round into D0; the carry flag receives a copy of D7 but takes no part in the rotation. It is a genuine 8-bit circular shift, and eight successive RLCs restore the original byte.
RAL, by contrast, makes the carry the ninth bit of the ring: D7 goes into the carry, and the old carry goes into D0. It takes nine RALs to return to the starting state, and the result depends on what the carry held beforehand — so the flag must be set or cleared deliberately before use.
Why the distinction matters in practice. The through-carry forms are what allow multi-byte shifts: rotate the low byte with RAL, and the bit that leaves it sits in the carry ready to enter the high byte on the next RAL, so a 16-bit or 32-bit quantity can be shifted a byte at a time. The 8-bit forms are for bit testing and for building masks, where wrapping within the byte is what is wanted.
A useful arithmetic aside : a left rotate multiplies by two and a right rotate divides by two, provided the bit rotated out is zero. This is how multiplication and division by powers of two are done on a processor with no multiply instruction — far faster than repeated addition.
All four are single-byte instructions affecting only the carry flag; the zero, sign and parity flags are left untouched, which occasionally surprises those expecting a shift to update them.
Hence, the correct code is a-iii, b-iv, c-i, d-ii.
Similar Questions
A microprocessor is a semiconductor chip fabricated with entire central processing unit (CPU) on it. It is a programmable device that accepts binary data from an input device, processes the data according to the instructions stored in the memory and provides results as output. Basically microprocessor performs two functions - (a) Fetches an instruction from the memory and (b) Performs the operation specified by the instruction. There are special inputs to the microprocessor called interrupts. External devices use these interrupts to get the microprocessor attention. A micro computer can be built by using 8085 microprocessor along with many other chips such as 8155, 8255, 8279, 8253, 8257, 8259, 8251 etc. 8085 microprocessor is 8-bit microprocessor which has 8-bit data registers where as 8086 is a 16-bit microprocessor.
The following 8051 assembly program is given. Answer the questions based on it.
Line No. Mnemonics 1 MOV SP, #4F H 2 SET B PSW.3 3 MOV R0, #25H 4 MOV R1, #0AH 5 MOV R2, #06H 6 PUSH 8 7 PUSH 9 8 PUSH 0AH . . . V V 20 POP 8 $D_7$ $D_6$ $D_5$ $D_4$ $D_3$ $D_2$ $D_1$ $D_0$ 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 :
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
Important Questions from Microprocessors
An 8086 address bus is a/an _____ -bit bus
Program counter for any counter:
In the pin out configuration of the 8085 microprocessor, the sequential input data is represented by
Which of the following functions is not performed by a microprocessor?
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
