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
After the execution of line 7 (PUSH 9) what is the address in the SP register and what is stored in stack memory location 51 H.
51H, 0AH
State of the register bank. With \(\texttt{SETB PSW.3}\) having selected bank 1, the registers map to internal RAM as R0 → 08H, R1 → 09H, R2 → 0AH, and lines 3–5 have loaded them:
| Register | Direct address | Contents |
|---|---|---|
| R0 | 08H | 25H |
| R1 | 09H | 0AH |
| R2 | 0AH | 06H |
Trace the pushes.
Line 6, \(\texttt{PUSH 8}\): SP goes 4FH → 50H, and the byte at address 08H (25H) is written to 50H.
Line 7, \(\texttt{PUSH 9}\): SP is pre-incremented 50H → 51H, and the byte at direct address 09H is written there. Address 09H holds 0AH (put there by \(\texttt{MOV R1, \#0AH}\)), so
\(51H \leftarrow 0AH, \qquad SP = 51H\)
Both parts of the answer therefore read 51H and 0AH.
The trap in this question. The value 0AH appears twice in the program in two completely different roles — as the data loaded into R1, and as the address of R2 in bank 1. Reading \(\texttt{PUSH 9}\) you must remember the operand 9 is an address (09H = R1), while the byte it contains, 0AH, is data. The distractors exploit exactly this: option 1 offers 25H (the previous push), option 2 gives an SP of 52H (one push too many), option 3 gives the previous SP with the new data.
Stack picture after line 7 (SP marks the top): 50H = 25H, 51H = 0AH ← SP.
Hence, after line 7 the SP register holds 51H and stack location 51H contains 0AH.
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 :
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.
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
