Which of the options in a multipurpose instruction used to implement the interrupt of 8085 and serial data input ?
SIM
Only one of the four is an instruction that does two jobs at once, and that is SIM — option 2.
What SIM does. Set Interrupt Mask takes the byte in the accumulator and uses it for two unrelated purposes, selected by different bits:
| Bit | Name | Function |
|---|---|---|
| D0 – D2 | M7.5, M6.5, M5.5 | Mask bit for each interrupt — 1 disables |
| D3 | MSE | Mask Set Enable — must be 1 for the mask bits to take effect |
| D4 | R7.5 | Resets the RST 7.5 flip-flop |
| D6 | SDE | Serial Data Enable |
| D7 | SOD | The serial bit output on the SOD pin |
The question is imprecisely worded and the answer is flagged accordingly. The 8085 has a matched pair of instructions, and each handles one direction of serial transfer:
SIM — sets the interrupt masks and sends serial output on the SOD pin.
RIM — reads the interrupt masks and receives serial input from the SID pin.
Strictly, an instruction dealing with interrupts and serial data input is RIM — which is not among the options. Of what is offered, SIM is the only multipurpose instruction of that family, and it is plainly the intended answer.
Why the other three cannot be right. SOD is not an instruction at all but a pin, driven by bit D7 of SIM. EJ is not an 8085 mnemonic in any form. RST 7.5 is a hardware interrupt input — one of the things SIM controls — not a multipurpose instruction; used as a mnemonic, RST n is a single-byte call instruction with no serial function whatever.
The elegance of the arrangement is that it gives the 8085 a serial port with no extra hardware. Software toggles SOD one bit at a time to transmit and samples SID to receive, so a bit-banged UART needs only two pins and a delay loop — enough for a serial console on a chip that has no serial peripheral built in.
Hence, the instruction is SIM.
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
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
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
