Lec-10: Unconditional Branching in 8085 | Microprocessor

Summary

This video script discusses the concept of unconditional branching in the 8085 microprocessor. It explains how the processor executes instructions sequentially unless a jump is required, which is determined without checking conditions. The script delves into the assembly language instructions like JMP, CALL, and RET, illustrating how they direct the flow of execution to specific memory addresses. It also touches on the addressing modes, particularly Immediate and Direct, and their impact on instruction size and execution. The explanation is technical, aimed at individuals with a background in computer architecture or programming.

Takeaways

• 😀 The video explains the concept of unconditional branching in the 8085 microprocessor.
• 📝 Unconditional branching means that the microprocessor will jump to a specific address without checking any conditions.
• 🔄 The instruction 'JMP' is used for unconditional branching, which directs the control to a particular address immediately after execution.
• 💡 The term 'LRET' is discussed, which stands for long return and is used in conjunction with 'JMP' to handle function calls and returns.
• 🔢 The size of the instruction in the 8085 microprocessor is detailed, with 'JMP' being 3 bytes and 'CALL' being 3 bytes, while 'RET' is only 1 byte.
• 📍 The difference between direct and immediate addressing modes is highlighted, with examples provided for each.
• 🚀 The video script uses the term 'IMMEDIATE' to describe the addressing mode where the jump is made directly to the address specified in the instruction.
• 💼 The concept of function calls and returns is explained, with emphasis on how control is transferred to the function and then back to the calling location.
• 🔧 The script provides a detailed breakdown of how the program counter is updated during the execution of branching instructions.
• 🧩 The video concludes with a discussion on addressing modes, clarifying that the direct addressing mode is not used for 'JMP' instructions as no data is copied from the address.

Q & A

What does the term 'unconditional branching' mean in the context of the 8085 microprocessor?

Unconditional branching refers to the process where the microprocessor jumps to a specific address without checking any conditions, regardless of whether the condition is true or not.

What is the significance of the instruction 'JMP' in the 8085 assembly language?

The 'JMP' instruction in 8085 assembly language is used to jump to a specified memory location, effectively changing the sequence of instruction execution to that location.

What does the term 'LDA' stand for in the context of the 8085 microprocessor?

In the context of the 8085 microprocessor, 'LDA' stands for 'Load Accumulator', which is an instruction that loads data from a specified memory address into the accumulator.

What is the purpose of the 'CALL' instruction in the 8085 microprocessor?

The 'CALL' instruction in the 8085 microprocessor is used to initiate a function call, transferring control to a new location in memory where the function is defined, and saving the return address for later use.

How does the 'RET' instruction work in the 8085 assembly language?

The 'RET' instruction in 8085 assembly language is used to return from a function or interrupt, typically after the function has completed its execution. It retrieves the return address from the stack and continues execution from that address.

What is the difference between 'JMP' and 'CALL' instructions in the 8085 microprocessor?

The 'JMP' instruction simply jumps to a new address without saving the return address, while the 'CALL' instruction not only jumps to a new address but also pushes the return address onto the stack for later retrieval with a 'RET' instruction.

What addressing mode is used when the address is provided directly in the instruction for a jump in the 8085 microprocessor?

When the address is provided directly in the instruction for a jump in the 8085 microprocessor, it is referred to as the 'Immediate Addressing Mode'.

What is the size of the 'JMP' instruction in terms of bytes in the 8085 microprocessor?

The 'JMP' instruction in the 8085 microprocessor is typically 3 bytes in size, as it includes the instruction opcode followed by a 16-bit address.

How does the 'CALL' instruction affect the program counter in the 8085 microprocessor?

After executing a 'CALL' instruction, the program counter in the 8085 microprocessor is updated to point to the address specified in the instruction, effectively transferring control to that location.

What is the significance of the 'C3' opcode in the 8085 microprocessor?

The 'C3' opcode in the 8085 microprocessor is associated with the 'JMP' instruction, indicating an unconditional jump to the address that follows the opcode.

What addressing mode is being referred to when the script mentions jumping to an address without checking any conditions?

The addressing mode being referred to when jumping to an address without checking any conditions is 'Immediate Addressing Mode', where the address is specified directly in the instruction.