Does 8080 Have General Purpose Registers

Registers of 8085 microprocessor

A microprocessor is a multipurpose, programmable, clock-driven, register-based electronic device that reads binary instructions from a storage device called memory, accepts binary information as input and processes information co-ordinate to those instructions and provide results as output. A 8085 microprocessor, is a second generation eight-bit microprocessor and is the base of operations for studying and using all the microprocessor available in the market.

Registers in 8085:

(a) General Purpose Registers –

The 8085 has half-dozen general-purpose registers to shop 8-bit information; these are identified as- B, C, D, East, H, and 50. These tin be combined every bit register pairs – BC, DE, and HL, to perform some 16-bit operation. These registers are used to store or copy temporary data, by using instructions, during the execution of the program.

(b) Specific Purpose Registers –

• Accumulator:
  The accumulator is an viii-bit annals (tin can store 8-flake information) that is the part of the arithmetic and logical unit (ALU). Later performing arithmetical or logical operations, the issue is stored in accumulator. Accumulator is also defined as register A.
• Flag registers:

  

  The flag register is a special purpose annals and it is completely different from other registers in microprocessor. It consists of 8 $.25 and only v of them are useful. The other three are left vacant and are used in the future Intel versions.These 5 flags are set or reset (when value of flag is 1, then it is said to be fix and when value is 0, then information technology is said to exist reset) later an operation according to data condition of the upshot in the accumulator and other registers. The five flag registers are:

  1. Sign Flag: It occupies the seventh bit of the flag register, which is also known equally the most pregnant bit. Information technology helps the programmer to know whether the number stored in the accumulator is positive or negative. If the sign flag is fix, it means that number stored in the accumulator is negative, and if reset, so the number is positive.
  2. Zip Flag:: Information technology occupies the sixth bit of the flag annals. It is set, when the operation performed in the ALU results in nothing(all 8 bits are zero), otherwise it is reset. It helps in determining if 2 numbers are equal or not.
  3. Auxiliary Carry Flag: It occupies the 4th bit of the flag register. In an arithmetic operation, when a carry flag is generated past the third fleck and passed on to the fourth bit, then Auxiliary Behave flag is set. If not flag is reset. This flag is used internally for BCD(Binary-Coded decimal Number) operations.

     Notation – This is the only flag register in 8085 which is non accessible by user.

  4. Parity Flag: It occupies the second flake of the flag register. This flag tests for number of i'due south in the accumulator. If the accumulator holds even number of 1'south, and so this flag is set and it is said to even parity. On the other hand if the number of 1'southward is odd, then information technology is reset and information technology is said to exist odd parity.
  5. Acquit Flag: Information technology occupies the zeroth bit of the flag register. If the arithmetics operation results in a carry(if consequence is more than 8 chip), and so Carry Flag is set; otherwise information technology is reset.

(c) Retention Registers –

At that place are two 16-scrap registers used to concord retention addresses. The size of these registers is 16 bits considering the retention addresses are 16 bits. They are :-

• Program Counter: This annals is used to sequence the execution of the instructions. The office of the plan counter is to point to the memory address from which the next byte is to exist fetched. When a byte (machine code) is being fetched, the plan counter is incremented past i to point to the next memory location.
• Stack Arrow: Information technology is used as a retention pointer. It points to a memory location in read/write retentiveness, called the stack. It is ever incremented/decremented by 2 during push and pop performance.

  Case –
  Here two binary numbers are added. The issue produced is stored in the accumulator. Now lets bank check what each bit means. Refer to the below explanation simultaneously to connect them with the instance.

  

  • Sign Flag (7th bit): Information technology is reset(0), which means number stored in the accumulator is positive.
  • Nada Flag (6th scrap): It is reset(0), thus outcome of the operations performed in the ALU is not-goose egg.
  • Auxiliary Carry Flag (4th bit): We tin can see that b3 generates a carry which is taken by b4, thus auxiliary behave flag gets ready (1).
  • Parity Flag (2d bit): Information technology is reset(0), it ways that parity is odd. The accumulator holds odd number of 1's.
  • Carry Flag (0th scrap): It is set(1), output results in more than 8 scrap.

Does 8080 Have General Purpose Registers,

Source: https://www.geeksforgeeks.org/registers-8085-microprocessor/

Posted by: bennettfactly.blogspot.com

Share this post