The program status word (PSW) is a register that performs the function of a status register and program counter, and sometimes more. The term is also applied to a copy of the PSW in storage.
What is meant by PSW in OS?
program status word (PSW) A collection of information that encapsulates the basic execution state of a program at any instant. It permits an interrupted process to resume operation after the interrupt has been handled.
What is PSW explain?
The Program Status Word (PSW) contains status bits that reflect the current CPU state. The 8051 variants provide one special function register called PSW with this status information. The 251 provides two additional status flags, Z and N, that are available in a second special function register called PSW1.
Why flag is also called PSW?
PSW (program status word) register
The two unused bits are user-definable flags . Four of the flags are called conditional flags, meaning that they indicate some conditions that result after an instruction is executed. These four are CY (carry), AC (auxiliary carry), P (parity), and OV (overflow).
Is PSW a register?
PSW (program status word) register The program status word (PSW) register is an 8-bit register . It is also referred to as the flag register. Although the PSW register is 8 bits wide, only 6 bits of it are used by the 8051. The two unused bits are user-definable flags.
How PSW is important for any microprocessor?
The PSW includes the instruction address, condition code, and other information to control instruction sequencing and to determine the state of the CPU. The active or controlling PSW is called the current PSW. The PSW is so important because it keeps track of the progress of the system and the executing program .
How many bits is a PSW?
| CY PSW. 7 Carry Flag | – PSW.1 User definable FLAG |
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What is the use of Pcon register?
The PCON or Power Control register, as the name suggests is used to control the 8051 Microcontroller’s Power Modes and is located at 87H of the SFR Memory Space. Using two bits in the PCON Register, the microcontroller can be set to Idle Mode and Power Down Mode. NOTE: PCON register is not bit addressable.
What do you mean by PSW in 8085?
PSW stands for PROGRAM STATUS WORD . PSW combines accumulator A and flag register F.
What is stored in the program counter?
The program counter (sometimes called instruction pointer) is a special-purpose register that contains the memory address of the next instruction to be executed . Every instruction is fetched from external memory at the address in the program counter, and stored in the instruction register.
What is carry flag in PSW?
PSW.7. Carry flag. The carry flag has two functions. Firstly, it is used as the carry-out in 8-bit addition/subtraction . For example, if the accumulator contains FDH and we add 3 to the contents of the accumulator (ADD A, #3), the accumulator will then contain zero and the carry flag will be set.
What is TCON register?
TCON ( Timer Control register ) TCON is an 8-bit register. Its bits are used for generating interrupts internal or external. ... TF0/TF1=> Timer 0/1 overflow flag when it is 1 it means timer is over flow. TH0/TL0 & TH1/TL1 These two registers TH and TL are timer high byte and timer low byte, 0 and 1 are the timers numbers.
What is auxiliary carry flag?
Auxiliary Carry Flag (AF) is one of the six status flags in the 8086 microprocessor . This flag is used in BCD (Binary-coded Decimal) operations. ... This flag is set to one if there is a CARRY from the lower nibble or BORROW for the lower nibble in binary representation. Else it is set to zero.
What is the difference between PC and DPTR?
Don’t forget that DPTR and PC refer to different logical address spaces; thus, depending on your physical memory implementation, DPTR=0x1234 may well address a different physical address location from PC=0x1234, etc! and exactly the same as hardware fetches the command byte.
What do you mean by flag register?
The FLAGS register is the status register that contains the current state of the CPU . The size and meanings of the flag bits are architecture dependent. ... The carry, parity, adjust, zero and sign flags are inherited from an earlier architecture, 8080 and 8085.
What is the configuration of PSW register?
The program status word (PSW) register is an 8-bit register, it is also referred to as the flag register the PSW register is 8-bit wide only 6-bit of it are used by the 8051, the two unused bits are user definable flags, four of the flags are called conditional flags, meaning that they indicate some conditions that ...
