What is xPSR?
xPSR is a generic term for a program status register. All unused bits in any individual or combined xPSR are Reserved. Figure 7.1 shows how the APSR, IPSR, and EPSR combine to form the PSR.
What are the 4 bit used in status register?
The Linux/ARM embedded platform ARM v6/v7 maintains a status register called the CPSR (current program status register) that holds four status bits, negative (N), zero (Z), carry (C), and overflow (O). These bits can be used for conditional execution of subsequent instructions.
What is flag of status register?
Common flags
| Flag | Name |
|---|---|
| Z | Zero flag |
| C | Carry flag |
| S / N | Sign flag Negative flag |
| V / O / W | Overflow flag |
What is the use of the Basepri register?
The special-purpose mask registers BASEPRI changes the priority level required for exception preemption. It has an effect only when BASEPRI has a lower value than the unmasked priority level of the currently executing software.
What is status bit?
Description. The Status Bits register is a collection of bits that provide a summary of the state of the axis. See the Registers Overview topic for details on how to address each specific bit in the various address formats.
What is SReg in AVR?
Status Register (SReg) : It is the flag register in the AVR micro-controller. It is a 8 – bit register. Only 6 of these 8 bits are called conditional flags. They are C, Z, N, V, S, H. The value of these bits indicates some conditions that result after the execution of an instruction.
What is the function of 0 8 bits of status register 0?
The representation of the 8 bits in the status register are: Bit 0: Carry Flag. Bit 1: Zero Flag.
What is Primask Faultmask and Basepri?
The PRIMASK, FAULTMASK, and BASEPRI registers are used for exception or interrupt masking. The PRIMASK register is a 1-bit wide interrupt mask register. When set, it blocks all exceptions (including interrupts) apart from the Non-Maskable Interrupt (NMI) and the HardFault exception. Priority level “-1”!
What is MSP and PSP?
Main Stack Pointer (MSP) is the default stack pointer. It is used in the Thread mode when the CONTROL bit[1] (SPSEL) is 0, and it is always used in Handler mode. • Processor Stack Pointer (PSP) is used in Thread mode when the CONTROL bit[1] (SPSEL) is set to 1.
Which bit is to be transferred to carry flag to check whether the NO is positive or negative?
Sign flag (S): The S flag is set to 1, when the result thus produced against any logical or arithmetic operations is negative, indicated by MS bit of 8-bit result being 1. It is reset to 0 otherwise if the result is positive, indicated by MS bit of 8-bit result being 0.
Which are different flags in PSW register?
8051 Flag Bits and PSW Register
| CY | PSW.7 | Carry Flag |
|---|---|---|
| RS0 | PSW.3 | Register Bank selector bit 0 |
| OV | PSW.2 | Overflow Flag |
| – | PSW.1 | User definable FLAG |
| P | PSW.0 | Parity FLAG. Set/ cleared by hardware during instruction cycle to indicate even/odd number of 1 bit in accumulator. |
Which register is MSP in ARM Cortex m3?
The Stack Pointer (SP) is register R13. In Thread mode, bit[1] of the CONTROL register indicates the stack pointer to use: 0 = Main Stack Pointer (MSP).
What is R13 in arm?
R13 is defined in the Thumb instruction set so that its use is primarily as a stack pointer. R13 is normally identified as Stack Pointer (SP) in Thumb instructions. In 32-bit Thumb instructions, if you use SP as a general purpose register beyond the architecturally defined constraints, the results are unpredictable.
Which bit position is used to check if a value is negative?
The most significant bit of a binary number is used to represent the sign bit. If the sign bit is equal to zero, the signed binary number is positive; otherwise, it is negative. The remaining bits represent the actual number.
How do you check if a number is negative with bits?
Check if a number is positive, negative or zero using bit operators in C++
- n is negative: 1 + (-1) – 0 = 0.
- n is positive: 1 + 0 – (-1) = 2.
- n is 0: 1 + 0 – 0 = 1.
How are the bits of the register PSW?
How are the bits of the register PSW affected if we select Bank2 of 8051? Explanation: Bits of PSW register are CY, AC, F0, RS1, RS0, OV, -, P so for selecting bank2 RS1=1 and RS0=0 which are fourth and third bit of the register respectively.
How can we make any bit of a register 0?
If we want to make any bit “0”, then we have to AND that bit with “0” so that the bit becomes “0”. We also have to AND the remaining bits of the register with “1” so that they remain unaltered.
How many registers are there in ARM Cortex M3?
13 general-purpose registers, r0-r12.
Does ARM have zero register?
The zero register (WZR/XZR) is used for a few encoding tricks. For example, there is no plain multiply encoding, just multiply-add. The instruction MUL W0, W1, W2 is identical to MADD W0, W1, W2, WZR which uses the zero register. Not all instructions can use the XZR/WZR.
What is R15 in ARM?
R15: PC (Program Counter). The Program Counter is automatically incremented by the size of the instruction executed. This size is always 4 bytes in ARM state and 2 bytes in THUMB mode. When a branch instruction is being executed, the PC holds the destination address.