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What will be the contents of PC after the execution of RST 4 Instruction?
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∙ 11y ago
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Justify RST instruction can be called 1 byte Call instruction?
The RST instruction is a 1 byte opcode with a 3 bit imbedded operand. There are 8 different RST instructions. Each pushes the PC on the stack, and loads the PC with the operand's value times 8. (0H, 8H, 10H, 18H, etc.)Pushing the PC on the stack and loading a new value into the PC is exactly what a CALL instruction does, so the RST instruction is a 1 byte CALL instruction. The difference between RST and CALL is that CALL is a 3 byte instruction which can go anywhere in memory in one instruction.
If the 8085 MPU fetches 2057H what is the content of PC?
The instruction 20H is RIM (Read Interrupt Mask). The instruction 57H is MOV D,A. The contents of PC after these two instruction will be 2 greater than it was before starting.
What is the use of Interrupt vector table of 8086 microprocessor?
The interrupt vector table in the 8085 is a region of low memory that contains the target addresses for the RST instructions. RST can be invoked by the program, by an INTR request which provides an RST x instruction in response to INTA, or by one of the four direct interrupt pins, TRAP, RST5.5, RST6.5, and RST7.5 Each of these interrupt sequences place the PC on the stack, and then execution goes to one of the vectors. The vectors are as follows... RST 0: 0000H RST 1: 0008H RST 2: 0010H RST 3: 0018H RST 4: 0020H TRAP: 0024H RST 5: 0028H RST5.5: 002CH RST 6: 0030H RST6.5: 0034H RST7: 0038H RST7.5: 003CH
How ISR is serviced?
when interrupt occurs, the program counter content will stores into stack, an PC will load interrupt address for next instruction execution. ofter completion ISR process PC will retrieves the stack values and execution will be continued.
What is execute cycle in microprocessor?
The sequence of operations that the cpu has to carry out while execution is called instruction cycle. 1:- Read an Instruction 2:- Decode the instruction 3:- Find the address of operand 4:- retrieve an operand 5:- perform desired operation 6:- find the address of destination 7:- store the result into the destination
How many interrupts in 8085 microprocessor?
The processor has 5 interrupts. They are presented below in the order of their priority (from lowest to highest):INTR is maskable 8080A compatible interrupt. When the interrupt occurs the processor fetches from the bus one instruction, usually one of these instructions:One of the 8 RST instructions (RST0 - RST7). The processor saves current program counter into stack and branches to memory location N * 8 (where N is a 3-bit number from 0 to 7 supplied with the RST instruction).CALL instruction (3 byte instruction). The processor calls the subroutine, address of which is specified in the second and third bytes of the instruction.RST5.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 002Ch (hexadecimal) address.RST6.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 0034h (hexadecimal) address.RST7.5 is a maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 003Ch (hexadecimal) address.Trap is a non-maskable interrupt. When this interrupt is received the processor saves the contents of the PC register into stack and branches to 0024h (hexadecimal) address.All maskable interrupts can be enabled or disabled using EI and DI instructions. RST 5.5, RST6.5 and RST7.5 interrupts can be enabled or disabled individually using SIM instruction.
Which register in 8086 contains the address of the next instruction to be fetched?
program counter holds the address of the next instruction.
What are the four distinct actions that a machine instruction can specify?
• The processor fetches the instruction from memory • Program counter (PC) holds address of the instruction to be fetched next • PC is incremented after each fetch • Fetched instruction loaded into instruction register
Why contents of a program counter change?
The PC (program counter) is a CPU memory variable, commonly called a "register," that the CPU uses to track where the current executing instruction is located in memory, or on some CPUs, where the next instruction to execute is. Without a PC, the CPU would not know where the code it is currently executing is stored, and thus would not be able to run programs.
What is the function of the instruction counter?
There is no such thing as an instruction counter. You are either referring to the instruction register (IR) or the program counter (PC), The PC is more commonly known as the instruction pointer (IP). The IR and IP work together. The IR fetches the instruction currently pointed to by the IP which is then incremented to refer to the next instruction. The IR is then decoded and executed and the cycle repeats ad infinitum (known as the fetch-decode-execute cycle). However, if the fetched instruction is a control transfer instruction (such as JMP), its execution will cause the IP to refer to another address which, in turn, causes execution to "branch" to a new section of code on the next fetch-decode-execute cycle. Note that a low-level JMP is equivalent to a goto statement in high-level code, however code can also branch through high-level if and switch statements as well as structured loops such as for, while and do-while statements.
What happens when branch instruction comes in 8086?
When a branch (or "jump") instruction is executed, the condition codes bits (in the flag register) determine whether or not the Program Counter (PC register) is changed to the Effective Address specified by the instruction; if not, then the PC is unchanged.
What is the function of the PC register in the 8086 CPU?
There is no PC register in the 8086/8088. It is called the IP register by Intel and it stands for the Instruction Pointer. It contains the address of the current/next instruction to be executed.
