The high order register of a register pair One of the registers A, B, C, D, E, H or LĪppearing at the end of the group of digits specifies hexadecimal, e.g. The symbol and abbreviations which have been used while explaining Intel 8085 instructions are as follows: Symbol/Abbreviations
There is a set of five flip-flops which indicate status (condition) arising after the execution of arithmetic and logic instructions. Such instructions do not require the address of the operand. There are certain instructions which operate on the content of the accumulator. 2500 is 16-bit data which is given in the instruction itself. LXI H, 2500 is an example of immediate addressing. In this addressing mode, the operand is specified within the instruction itself. The address of the memory resides in H-L pair and this has already been specified by an earlier instruction in the program, i.e. The address of the memory is not directly given in the instruction. For this instruction, the operand is in the memory. In the above program the instruction MOV A, M is an example of register indirect addressing. MOV A, M - Move the content of the memory location, whose address is in H-L pair (i.e.LXI H, 2500 H - Load H-L pair with 2500H.In Register Indirect mode of addressing, the address of the operand is specified by a register pair.
#OPCODE SHEET FOR 8086 PDF CODE#
0 1 are for MOV operation, the next three bits 1 1 1 are the binary code for register A, and the last three bits 000 are the binary code for register B. The opcode 78H can be written in binary form as 01111000. Besides the operation to be performed the opcode also specifies source and destination registers.
MOV A, B: Move the content of B register to register A. The opcode specifies the address of the register(s) in addition to the operation to be performed. In register addressing mode, the operand is in one of the general purpose registers. Here, it is understood that the source of the data is accumulator. The 2nd and 3rd bytes of the instruction specify the address of the memory location. In this instruction, 2400H is the memory address where data is to be stored. STA 2400H: It stores the content of the accumulator in the memory location 2400H.ģ2, 00, 24: The above instruction in the code form. In this addressing mode, the address of the operand (data) is given in the instruction itself. Intel 8085 uses the following addressing modes: These techniques are called addressing modes. There are different techniques to specify data for instructions. It may 1-byte, 2-byte or 3-byte instruction.Įach instruction requires some data on which it has to operate. The most instructions of this type operate on the content of the accumulator.ĭue to different ways of specifying data for instructions, the machine codes of all instructions are not of the same length. In some instructions, data is implied.The contents of the registers are the required data. Some instructions specify two registers.The content of the specified register is one of the operands. In some instructions, only one register is specified.The address of the memory location, I/O port or I/O device, where data resides, may be given in the instruction itself.8-bit or 16-bit data may be directly given in the instruction itself.The various techniques to specify data for instructions are: Next → ← prev Instruction Set of 8085 Instruction and Data Formats
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