Skip to main content

Logical Group Instructions (Part-II) - ORA and ORI

By
ORA R: 
  • This instruction logically OR the contents of the specified register with the contents of the accumulator.
  • Register R can be any 8-bit general purpose register like A, B, C, D, E, H and L.
  • The result is stored in the accumulator.
  • S (Sign flag), Z (Zero flag), P (Parity flag) are modified.
  • CY (Carry flag) and AC (Auxiliary Carry flag) are reset.
  • It is a one byte instruction.
  • Register addressing mode is used.
Example:
If A = 1010 1011 = ABH and L = 1000 0111 =87H
ORA L ; This instruction will logically OR  the contents of A (ABH) with the contents of L (87H) and the result (AFH) is stored in A.

ORA M:
  • This instruction logically OR the contents of the memory location pointed by HL register pair with the contents of the accumulator.
  • The result is stored in the accumulator.
  • S (Sign flag), Z (Zero flag), P (Parity flag) are modified.
  • CY (Carry flag) and AC (Auxiliary Carry flag) are reset.
  • It is a one byte instruction.
  • Register indirect addressing mode is used.
Example:
If HL = 3000H, (3000H) = 0110 0101 = 65H and A = 0111 1000 = 78H
ORA M ; This instruction will logically OR  the contents of A (78H) with the contents of location 3000H i.e. 65H and the result (7DH) is stored in A.

ORI 8-bit data:
  • This instruction logically OR the 8-bit data given in the instruction itself with the contents of the accumulator.
  • The result is stored in the accumulator.
  • S (Sign flag), Z (Zero flag), P (Parity flag) are modified.
  • CY (Carry flag) and AC (Auxiliary Carry flag) are reset.
  • It is a two byte instruction.
  • Immediate addressing mode is used.
Example:
If A = 1101 0100 = D4H
ORI 0FH ; This instruction will logically OR  the contents of A (D4H) with 0FH and the result (DFH) is stored in A.

NOTE: OR instruction is used to set any bit in a binary number.

Labels:

Comments

Post a Comment

Popular posts from this blog

Program to pack the two unpacked BCD numbers

By
Statement: Pack the two unpacked BCD numbers stored in memory locations 2000H and 2001H and store the result in memory location 2002H. The least significant digit is stored at 2000H. Example: (2000H) = 04H (2001H) = 09H Result = (2002H) = 94H Program: LDA 2001H                        ; Obtain the most significant BCD digit RLC                                    ; Rotate left  RLC                                    ; Rotate left  RLC                                    ; Rotate left  RLC                                    ; Rotate left...
Post a Comment
Read more

Program to exchange the contents of two memory locations

By
Statement: Exchange the contents of memory locations 2000H and 2001H. Example:  Initially, (2000H) = 34H (2001H) = 20H After exchanging, (2000H) = 20H (2001H) = 34H Program 1 using direct addressing instructions: LDA 2000H               ; Get the contents of location 2000H into accumulator MOV B, A                  ; Move the contents of accumulator into register B LDA 2001H                ; Get the contents of location 2001H into accumulator STA 2000H                 ; Store the contents of accumulator into location 2000H MOV A, B                  ; Move the contents of register B into accumulator STA 2001H                 ; Store the contents of accumulator into location 2001H HLT  ...
Post a Comment
Read more

Stack Operations Instructions (Part-II) - SPHL and XTHL

By
SPHL: This instruction copies the contents of HL register pair to the stack pointer (SP). It means that the stack pointer will now point to the memory location whose address was given in the HL register pair. No flags are affected. It is a one byte instruction. Register addressing mode is used. Example: If HL = 2030H, then SPHL ; This instruction will copy 2030H into SP. So SP will point to the memory location 2030H. XTHL: This instruction exchanges the contents of the memory location pointed by stack pointer with the contents of the L register and the contents of the next memory location with the contents of H register. This instruction does not alter the contents of the stack pointer. No flags are affected. It is a one byte instruction. Register Indirect addressing mode is used. Example: If HL = 5601H, SP = 2000H, (2000H) = 30H and (2001H) = 20H, then XTHL ; This instruction will exchange the contents of the memory location 2000H i.e. 3...
Post a Comment
Read more