8086 opcode table

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By using our website and services, you expressly agree to the placement of our performance, functionality and advertising cookies. Please see our Privacy Policy for more information. Register Usage Use in Real Mode Register Use in Virtual Mode Use in-bit microprocessor designed for applications needing very high performance and optimized for multitasking operatingFigure Abstract: microprocessor flag register Microprocessor interrupts opcode table for microprocessor bytes and string manipulation of opcode for INTEL microprocessor opcode table for microprocessor effective address calculation microprocessor is called parallel processor Opcode list of microprocessor Text: in Table 3.

Table 3. Real Mode issignals for each byte of the data bus. It is ideal for both desktop and battery-powered portable personal computers. For portables, the AmDXL microprocessorhardware and software for the based personal computers. For portables, the AmDXL microprocessor 's true static design offers longerfor the based personal computers.

The AmDXL microprocessor is your solution to meet the demand for high-performance, bit desktop and portable personal computers.

Table summarizes these differences. See Section 4 Protected Mode Architecture for. Abstract: d microprocessor pin out diagram microprocessor block diagram and pin diagram opcode sheet free Programmers Reference Manual Opcode list of microprocessor Text:protected mode, or virtual- mode. All memory access is handled by the Intel DX Microprocessor ; the. Abstract: bts - 1b microprocessor application seven segment opcode sheet a a opcode for password based door lock interface with microprocessor paging mechanism A Text: application software for use with products from the Am microprocessor family.

Abstract: No abstract text available Text: Table 2. Abstract: opcode table for microprocessor SXL microprocessor paging mechanism microprocessor pin out diagram microprocessor features amDX SXL SX notebook microprocessor flag register Text: instruction prefixes.

Table 5 summarizes the possible interrupts for the AmSXL microprocessor and showsmicroprocessor is in a state that permits restart ot the instruction, for all cases by those given in Table 7microprocessor is a high-speed, true static implementation of the Intel iSX.

It is ideal for both desktop and battery-powered notebook personal computers. Pin 1 is marked for orientation. Abstract: No abstract text available Text:. All memory access isto the processing mode of the Intel DX Microprocessor. Abstract: amDX and amdx 40 memory interfacing to mp microprocessor rom 32 kb design 4k ram 8k rom 16p 20f microprocessor introduction microcomputer microprocessor memory organisation Text: instruction prefixes.

AmSX Microprocessor Registers. It, or virtual- mode. Table 2. The microprocessor brings the TM math coproc essor on-chip.

All software written for theimplement a virtual memory system, the microprocessor supports full restartability for all page andProtected Mode. In Real Mode the microprocessor operates as a very fast Real Mode is required. Base and Index Registers for 16instruction prefixes.

For portables, the AmDXL microprocessor 's true staticallows for a standby mode. For additional information see Clock. See Bus Control Signals for additional information. Abstract: No abstract text available Text: Connect Figure 1. Alphabetical PinSX Microprocessor.

NAMicroprocessor.

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See Coprocessor Interface Signals for additional information.The following table provides a list of xAssembler mnemonics, that is not complete.

Most of them can be found, for others see at www. The high order nibble is zeroed. Multiplies AH by 10 and the adds result into AL. Sets AH to zero. This instruction is also known to have an undocumented behavior. The high order nibble of each byte must be zeroed before using this instruction. High order nibble is zeroed. If CF is set, a 1 is added to the destination.

Both operands are binary. Otherwise the Zero Flag is cleared. Interrupt 5 occurs if the source value is less than or higher than the source.

Sets ZF if a bit is found set and loads the destination with an index to first set bit. Clears ZF is no bits are found set. Result left in destination register is undefined if the operand is a 16 bit register. Code continues with execution at CS:IP. NMI's and software interrupts are not inhibited. This is a privileged operation and is generally used only by operating system code. Flags can subsequently be checked for conditions. Updates flags based on the subtraction and the index registers E SI and E DI are incremented or decremented depending on the state of the Direction Flag.

The REP prefixes can be used to process entire data items. If equal the "dest" is loaded with "src", otherwise the accumulator is loaded with "dest". Contents of AL are changed to a pair of packed decimal digits. If the source divisor is a byte value then AX is divided by "src" and the quotient is placed in AL and the remainder in AH.

Operand "locals" specifies the amount of storage to be allocated on the stack.This reference is intended to be precise opcode and instruction set reference including x Its principal aim is exact definition of instruction parameters and attributes.

In contrast to other references, primary source of this reference is an XML document, which guarantees clear and structured information base and therefore ability to extract many various informations such as a list of instructions from requested groups, etc. The reference is primarily based on Intel manuals as Intel is the originator of x86 architecture. Additionally, it describes undocumented instructions as well. On appropriate places, it gives a notice if an opcode act differently on AMD architecture.

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Support for Cyrix, NexGen etc. These editions are available at the moment: The coder suite is intended to more common use and contains the following editions: coder32coder64and coder sorted by opcodeand coderabccoderabcand coder-abc sorted by mnemonic. The geek suite is intended for deeper research of x86 architectures' instruction set.

This includes geek32geek64and geek editions by opcode and geekabcgeekabcand geek-abc editions by mnemonic. More on the purpose and use of this suite see close below. Don't get confused by geek -abc and coder -abc editions. Both of them contains instruction set of both x and x architectures.

If you don't have a particular reason to use them such as to view the differencies between the architecturesthe other editions would probably suit you better. Editions coder32 a geek32 relate exclusively to x architecture. Similarly, editions coder64 and geek64 relate exclusively to x architecture.

The geek editions contains as much complete information from the source XML document as possible. That's why they may seem quite unclear. You appreciate them only if you need to get to know the instruction set deeply or if you investigate the source XML and you need to visualize it better. These editions use specific operand codes which are described in Instruction Operand Codes chapter below.

8086 opcode table

These codes may look strange and obscure at the first sight. The reason to use them is that they hold more information than the more common ones. One can determine that the destination operand is either axeaxor raxand the source one is either imm16 or imm If one is just getting started with x64 architecture, it is not clear how exactly is bit immediate added to bit rax.

The immediate value is encoded there using Ivds code.

Intel x86 Assembler Instruction Set Opcode Table

I code means Immediatev means word or doubleword imm16 or imm The most important part is ds code, which means doubleword, sign-extended to 64 bits for bit operand size. Now is it clear. As for Itanium-specific instructions, they are added just for the sake of interest - they give a notice that the appropriate opcodes are already used.This is an HTML-ized version of the opcode map for the processor. A plain-text version - easily parsable by software - is also available.

This map was constructed by taking a map for a more recent x86 processor and removing information irrelevant to the much earlier processor. I wanted as simple a map as possible, and, to that end, this map contains some lacunae:.

In addition to the information that was removed, this map contains two known errors.

8085 instruction set with opcodes - arithmetic and data transfer -

To use the map, find the cell in the row labelled with the opcode's most significant 4 bits, and the column labelled with the opcode's least significant 4 bits. The map is split in half; columns appear in the first partwhile columns 8-F appear in the second. Arguments are either a pair of letters - the first in upper case, the second in lower case - or a special symbol. Other special symbols can be looked up in the " Special Argument Codes " table.

Both operands are of type "v", so both are WORDs. SI turns out to represent as one might expect the bit SI register, so opcode 4E simply decrements this register by 1. Yes, with nearly 30 years hindsight, there probably shouldn't be an entire opcode devoted to this operation. The one remaining complexity involves "group" opcodes, such as To disassemble "group" opcodes, consult the " Opcode Extensions " table for any entry in the opcode map with a mneumonic of the form GRP. Note that arguments may be specified in both the opcode map and the opcode extensions table e.

Normally, however, the arguments from the opcode map are used. As far as I know, this opcode map is, modulo the lacunae and errata mentioned above, correct.

8086 OPCODE

However, if you see something that doesn't look right, please contact me. If you're interested in reading more about the disassembler, the following posts might be worth a look:. Direct address. Applicable, e. The operand is either a general-purpose register or a memory address. If it is a memory address, the address is computed from a segment register and any of the following values: a base register, an index register, a displacement.

The instruction contains a relative offset to be added to the address of the subsequent instruction. Byte argument.

8086 opcode table

Unusual in that arguments of this type are suppressed in ASM output when they have the default value of 10 0xA.

Word argument. The 'v' code has a more complex meaning in later x86 opcode maps, from which this was derived, but here it's just a synonym for the 'w' code. A constant argument of 1, implicit in the opcode, and not represented elsewhere in the instruction. A constant argument of 3, implicit in the opcode, and not represented elsewhere in the instruction.X86 assembly instructions have a one-to-one relationship with the underlying machine instructions.

This means that essentially we can convert assembly instructions into machine instructions with a look-up table. This page will talk about some of the conversions from assembly language to machine language. The x86 architecture is a complex instruction set computer CISC architecture. Amongst other things, this means that the instructions for the x86 architecture are of varying lengths. This can make the processes of assembly, disassembly and instruction decoding more complicated, because the instruction length needs to be calculated for each instruction.

The length is defined separately for each instruction, depending on the available modes of operation of the instruction, the number of required operands and more. Not all instructions have W or D bits; in some cases, the width of the operation is either irrelevant or implicit, and for other operations the data direction is irrelevant.

8086 opcode table

Notice that Intel instruction format is little-endian, which means that the lowest-significance bytes are closest to absolute address 0. Thus, words are stored low-byte first; the value H is stored in memory as 34H 12H. By convention, most-significant bits are always shown to the left within the byte, so 34H would be B.

Normally, this would be expected to be the operand [BP]. However, instead the bit displacement is treated as the absolute address.

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Note that this is XORing CL with the contents of address 12H — the square brackets are a common indirection indicator. The opcode for XOR is "dw". D is 1 because the CL register is the destination. W is 0 because we have a byte of data.

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Our first byte therefore is "". Now, we know that the code for CL is Reg thus has the value Byte 2 is thus 00 b. Byte 3 and 4 contain the effective address, low-order byte first, H as 12H 00H, or b b. In this case, because there are no square brackets, 12H is immediate: it is the number we are going to XOR against. The opcode for an immediate XOR is w; in this case, we are using a byte, so w is 0.

So our first byte is b. We already know that the register value for CL isso our second byte is 11 b. The third byte and fourth byte, if this were a word operation are the immediate data. The bit instructions are encoded in a very similar way to the bit instructions, except by default they act upon dword quantities rather than words. Beginning with the opcode byte first, it remains the same, 32H.

Consulting the Intel IA manual, Volume 2C, Chapter 5, "XOR"--we see this opcode defines that a it requires 2 operands, b the operands have a direction, and the first operand is the destination, c the first operand is a register of 8-bits width, d the second operand is also 8-bit but can be either a register or memory address, and e the destination register CL will be overridden to contain the result of the operation.

It doesn't look like we need any prefix bytes to get the operand sizes we want. We know the first operand is going to be our destination register. Next we look for an Effective Address formula which matches our second operand, which is a displacement with no register and therefore no segment, base, scale, or index.

The nearest match is going to be disp32, but reading the table is tricky because of the footnotes. Our second byte is therefore b or 0CH. So our third byte is now 25H.Saves procedure linking information on the stack and branches to the called procedure specified using the target operand. The target operand specifies the address of the first instruction in the called procedure. The operand can be an immediate value, a general-purpose register, or a memory location.

The latter two call types inter-privilege-level call and task switch can only be executed in protected mode. Near Call. When executing a near call, the processor pushes the value of the EIP register which contains the offset of the instruction following the CALL instruction on the stack for use later as a return-instruction pointer. The processor then branches to the address in the current code segment specified by the target operand.

The target operand specifies either an absolute offset in the code segment an offset from the base of the code segment or a relative offset a signed displacement relative to the current value of the instruction pointer in the EIP register; this value points to the instruction following the CALL instruction. The CS register is not changed on near calls.

The operand-size attribute determines the size of the target operand 16, 32 or 64 bits. When in bit mode, the operand size for near call and all near branches is forced to bits. If the operand size attribute is 16, the upper two bytes of the EIP register are cleared, resulting in a maximum instruction pointer size of 16 bits.

When accessing an absolute offset indirectly using the stack pointer [ESP] as the base register, the base value used is the value of the ESP before the instruction executes. A relative offset rel16 or rel32 is generally specified as a label in assembly code. But at the machine code level, it is encoded as a signed, or bit immediate value. In bit mode the relative offset is always a bit immediate value which is sign extended to bits before it is added to the value in the RIP register for the target calculation.

As with absolute offsets, the operand-size attribute determines the size of the target operand 16, 32, or 64 bits. In bit mode the target operand will always be bits because the operand size is forced to bits for near branches. When executing a far call in real- address or virtual mode, the processor pushes the current value of both the CS and EIP registers on the stack for use as a return-instruction pointer.

The target operand specifies an absolute far address either directly with a pointer ptr or ptr or indirectly with a memory location m or m With the pointer method, the segment and offset of the called procedure is encoded in the instruction using a 4-byte bit operand size or 6-byte bit operand size far address immediate.

With the indirect method, the target operand specifies a memory location that contains a 4-byte bit operand size or 6-byte bit operand size far address.Is there any method to rebuild an microprocessor instruction from its opcode?

Also how can we convert the instruction to the opcode? I am trying to build an emulator, and cannot continue without knowing these. Thanks in advance.

Generally, the structure of the instructions in microprocessor has 4 parts.

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Label, Opcode, Operand, Comments. Here the label is the starting part of the code that can be a number or a symbol. Label is assigned the current value of the active location counter and serves as an instruction operand. Opcodes are also known as operational code or the opstring.

They define the function that needs to be carried on the input variables. Operands are trhe input variables. And comments are the remarks given at the end of the instruction for ease of understanding.

Opcode conversion is nothing but the translation to binary digits. Every opcode has its binary equivalent. About Us. Contact Us. Question asked by Len in Electronics on Oct 27, Feed Ask New Question.

Posted in: Electronics. I think firstly you have to maintain a mapping between you opcodes and instructions.


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