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Conditional loop instructions typically test the Zero Flag (ZF) and the Carry Flag (CF) to determine the outcome of comparisons or arithmetic operations. The Zero Flag indicates whether the result of an operation is zero, while the Carry Flag is used for unsigned comparisons to indicate if a value has exceeded its range. Additionally, the Sign Flag (SF) and Overflow Flag (OF) may also be tested depending on the specific type of comparison being performed. These flags help decide whether to continue iterating or to exit the loop.
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How compare instruction is used in 8085?
The compare and subtract instructions in the 8085 both subtract one operand from another, and set flags accordingly. The subtract instruction stores the result in the accumulator, while the compare instruction does not - except for the flags, the compare instruction "throws" the result away.
Which instruction format lists a set of conditions and meanings?
The instruction format that lists a set of conditions and meanings is typically referred to as a "condition code" or "status register" format. This format defines the various flags or conditions that indicate the state of the processor, such as zero, carry, overflow, or negative. Each condition corresponds to specific outcomes of operations, enabling conditional execution of instructions based on these status flags. This is commonly used in assembly language and architecture documentation.
What is instruction format of cmp?
The instruction format of the CMP (compare) instruction varies by architecture, but generally, it follows a similar structure across different assembly languages. Typically, it includes an opcode followed by two operands, which can be registers, immediate values, or memory locations. The CMP instruction compares the values of the operands and sets the processor flags (such as Zero Flag, Sign Flag, and Carry Flag) based on the result, without modifying the actual values. This allows subsequent conditional instructions to determine the flow of control based on the comparison.
What are the instruction to reset RST 7.5?
To reset the pending RST 7.5 instruction in the 8085, you need to execute a SIM instruction with a particular value in the accumulator. PUSH FLAGS MVI A,10H SIM POP FLAGS Of course the PUSH and POP are optional, if you don't need to preserve the value of the accumulator.
Which registers are changed by the cmp instruction?
MP Compares the first source operand with the second source operand and sets the status flags in the EFLAGS register according to the results. The comparison is performed by subtracting the second operand from the first operand and then setting the status flags in the same manner as the SUB instruction. When an immediate value is used as an operand, it is sign-extended to the length of the first operand. So, only the flags are affected. Operation: temp = Source1 - SignExtend(Source2); ModifyStatusFlags(); //Modify status flags in the same manner as the SUB instruction Flags affected: The CF, OF, SF, ZF, AF, and PF flags are set according to the result.
What is the effect of operating different instruction on psw in 8085?
In the 8085 microprocessor, the Program Status Word (PSW) contains important flags that reflect the state of the processor. Different instructions can affect these flags, such as the Zero Flag, Sign Flag, Carry Flag, and Parity Flag. For example, arithmetic operations like addition or subtraction can set or reset these flags based on the result of the operation. Consequently, the PSW is essential for conditional branching and decision-making within programs, as it provides the necessary status information determined by the executed instructions.
What is function of nop in microprocessor?
The NOP instruction is short for no-operation. It is an executable instruction that does nothing to the processor, its registers, or its flags. It is useful in timing loops, or to provide room for patchabilty of a piece of code.
What is the difference between conditional and control flags in 8086 microprocessor?
Control Flag Register: The Control Flag Register (CFR), also known as the Program Status Word (PSW), is a register used to control the execution flow and behavior of the processor. It typically stores various control flags that govern different aspects of the CPU's operation. Some common flags found in the Control Flag Register include: Carry Flag (CF): Used to indicate whether an arithmetic operation generated a carry or borrow. Zero Flag (ZF): Indicates whether the result of an operation is zero. Sign Flag (SF): Indicates the sign (positive or negative) of the result. Overflow Flag (OF): Indicates whether an arithmetic operation resulted in an overflow. Interrupt Flag (IF): Determines whether interrupts are enabled or disabled. The Control Flag Register provides control over program execution, including branching, interrupt handling, and arithmetic operations. It helps determine the outcome of operations and can be used for conditional branching based on specific flag states. Conditional Flag Register: The Conditional Flag Register (CFR), also known as the Condition Code Register (CCR) or Status Register (SR), contains flags that reflect the result of the most recent arithmetic or logical operation performed by the processor. These flags are used to perform conditional branching and control the flow of instructions based on specific conditions. The flags present in the Conditional Flag Register can vary depending on the processor architecture, but some common flags include: Zero Flag (ZF): Indicates whether the result of an operation is zero. Sign Flag (SF): Indicates the sign (positive or negative) of the result. Overflow Flag (OF): Indicates whether an arithmetic operation resulted in an overflow. Carry Flag (CF): Used to indicate whether an arithmetic operation generated a carry or borrow. Auxiliary Carry Flag (AF): Indicates a carry or borrow from the lower-order nibble (4 bits) to the higher-order nibble. The Conditional Flag Register is primarily used for conditional jumps or branches, allowing the processor to alter the program flow based on the current flag states. To summarize, the Control Flag Register focuses on controlling the processor's behavior and handling interrupts, while the Conditional Flag Register reflects the outcome of arithmetic and logical operations and enables conditional branching based on flag states.
Why in INR instruction no flags are modified?
In the INR (Increment Register) instruction, the operation increments the value of a specified register by one. This instruction does not modify any flags because it does not affect the status of the zero flag or the sign flag in a way that would be relevant for subsequent operations. Specifically, the zero flag is set only if the result is zero, which does not apply to an increment operation, while the sign flag does not change in a predictable manner either. Therefore, the design choice is made to keep the flags unchanged to avoid unnecessary complications in the execution flow.
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What type of flags in 8086 and 8088 microprocessor and their uses.?
There are nine flags in the 8086/8088.SF - Sign Flag - The result is negativeZF - Zero Flag - The result is zeroAF - Auxillary Carry Flag - A BCD carry occurredPF - Parity Flag - Indicates the oddness or evenness of the number of bitsCF - Carry Flag - An unsigned carry occurredOF - Overflow Flag - A signed overflow/carry occurredDF - Direction Flag - Controls the direction of repeated string operationsIF - Interrupt Flag - Enables or disables interruptsTF - Trace Flag - Controls the debug single step interruptIn general, most of these flags are set as a result of some arithmetic or logical instruction and can be tested using the conditional branch instructions. Exceptions are DF, which controls the directionality of repeated string operations, IF, which controls interrupts, and TF, which controls debugging.
what type of flags in 8086 and 8088 microprocessor and their uses?
There are nine flags in the 8086/8088.SF - Sign Flag - The result is negativeZF - Zero Flag - The result is zeroAF - Auxillary Carry Flag - A BCD carry occurredPF - Parity Flag - Indicates the oddness or evenness of the number of bitsCF - Carry Flag - An unsigned carry occurredOF - Overflow Flag - A signed overflow/carry occurredDF - Direction Flag - Controls the direction of repeated string operationsIF - Interrupt Flag - Enables or disables interruptsTF - Trace Flag - Controls the debug single step interruptIn general, most of these flags are set as a result of some arithmetic or logical instruction and can be tested using the conditional branch instructions. Exceptions are DF, which controls the directionality of repeated string operations, IF, which controls interrupts, and TF, which controls debugging.
