Microprocessor Instruction Set

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Questions and Answers

What is the opcode for the instruction ADD M?

86 (correct)

What is the opcode for the instruction MVI A, 7FH?

3E (correct)

What is the opcode for the instruction JMP 9050H?

C3 (correct)

What is the opcode for the instruction LDA 8850H?

3A Signup and view all the answers

What is the size of each RAM chip in the IC 6116?

2 K x 8 Signup and view all the answers

What is the opcode for the instruction MOV A, B?

78 Signup and view all the answers

How many address lines does the IC 6116 have?

11 Signup and view all the answers

What is the opcode for the instruction ADI 0FH?

C6 Signup and view all the answers

What is the machine code for the instruction ADD M?

86 Signup and view all the answers

What is the purpose of the 74LS138 decoder in the interfacing of IC 6116 RAM chips?

To select the correct RAM chip based on the address signals Signup and view all the answers

What is the machine code for the instruction MVI A, 7FH?

3E 7F Signup and view all the answers

What is the address range for RAM chip 1 in the IC 6116?

8000H - 87FFH Signup and view all the answers

What is the purpose of the IOR and IOW control signals in peripheral mapped I/O interfacing?

To activate input and output devices Signup and view all the answers

What is the instruction used to access an output device in peripheral mapped I/O interfacing?

OUT Signup and view all the answers

What is the purpose of the IO/M signal in peripheral mapped I/O interfacing?

To differentiate between I/O and memory operations Signup and view all the answers

What is the advantage of using peripheral mapped I/O interfacing?

It provides a separate address space for I/O devices Signup and view all the answers

What is the interrupt type of the NMI interrupt?

2 Signup and view all the answers

What is the use of the IRET instruction?

To return from an interrupt processing routine Signup and view all the answers

What is the purpose of the INTO instruction?

To generate an interrupt on overflow Signup and view all the answers

What is the type of the single-step interrupt?

1 Signup and view all the answers

What is the purpose of the INT instruction?

To generate a software interrupt Signup and view all the answers

What is the effect of setting the TF flag?

It generates a single-step interrupt Signup and view all the answers

What is the type of the Divide Error interrupt?

0 Signup and view all the answers

What is the purpose of the STI instruction?

To enable maskable interrupts Signup and view all the answers

Study Notes

Instruction Set

One byte instructions:
- Opcode: MOV, Operand: A, B, Machine code/Hex code: 78
- Opcode: ADD, Operand: M, Machine code/Hex code: 86
Two byte instructions:
- Opcode: MVI, Operand: A, 7FH, Machine code/Hex code: 3E, 7F
- Opcode: ADI, Operand: 0FH, Machine code/Hex code: C6, 0F
Three byte instructions:
- Opcode: JMP, Operand: 9050H, Machine code/Hex code: C3, 50, 90
- Opcode: LDA, Operand: 8850H, Machine code/Hex code: 3A, 50, 88

Addressing Modes

Immediate addressing
Memory direct addressing
Register direct addressing
Indirect addressing
Specification of IC 6116:
- 2 K x 8 RAM
- 2 KB = 211 bytes
- 11 address lines

Interfacing

6116 chip address range: 8000H - 87FFH (chip 1) and 9000H - 97FFH (chip 2)
Interfacing with 8085 and 74LS138 decoder:
- A0 – A10 lines of 8085 connected to 11 address lines of RAM chips
- Three address lines of 8085 connected to select inputs (C, B, and A) of decoder
- Enable inputs of decoder connected to remaining lines of 8085

Peripheral Mapped I/O Interfacing

I/O devices treated differently from memory chips
Control signals: I/O read (IOR) and I/O write (IOW)
Generation of IOR and IOW signals shown in Fig. 20
IN instruction for accessing input device
OUT instruction for accessing output device

Addressing Modes (continued)

Based Indexed: contents of base register (BX or BP) + index register (SI or DI) = pointer to location
Based Indexed with displacement: base register + index register + 8-bit or 16-bit instruction operand = pointer to location

Interrupts

INTR: maskable hardware interrupt
NMI: non-maskable interrupt
Software interrupts: INT, INTO, and single-step interrupt
Interrupt types:
- 0: Divide Error
- 1: Single-step interrupt
- 2: NMI
- 3: Breakpoint interrupt
- 6: Unused opcode
- 7: Escape opcode
Interrupt processing: store FLAGS register, disable further interrupts, fetch interrupt type, and jump to interrupt processing routine

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Description

This quiz covers examples of one-byte and two-byte instructions in microprocessor programming, including opcodes, operands, and machine code.