Microcontroller Instruction Set. For interrupt response time information, refer to the hardware description chapter. Note: 1. Operations on SFR byte address. The instruction set is optimized for 8-bit control applications. It provides a variety of fast addressing modes for accessing the internal RAM to facilitate byte. Instructions. has about instructions. These can be grouped into the following categories. Arithmetic Instructions; Logical Instructions; Data.

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Archived from the original on 30 May Most systems respect this distinction, and so are unable to download and directly execute new programs. The operations specified by the most significant nibble are as follows. The low-order bit of the register bank. This page was last edited on 1 Decemberat The instrucgion bit of the register bank.

Carry bitC. Overflow flagOV. They were identical except for the non-volatile memory type. SUBB Adata. ORL Cbit. Set when addition produces a signed overflow. For other instructions it can be treated as another scratch pad register.

Embedded system Programmable logic controller.

8051 Instruction Set

inxtruction The SJMP short jump opcode takes the signed relative offset byte operand and transfers control there relative to the address of the following instruction. XRL Adata. For the latter, there are explicit instructions to jump on whether or not the accumulator is zero. That means an compatible processor can now execute million instructions per second. From Wikipedia, the free encyclopedia. Some derivatives integrate a digital signal processor DSP.


Intel MCS-51

There are various high-level programming language compilers for the RLC A rotate left through carry. MOV Adata.

In other projects Wikimedia Commons. JBC bitoffset jump if bit set with clear. More than 20 independent manufacturers produce MCS compatible processors.

These registers also allowed the to quickly perform a context switch. Single-board microcontroller Special function register.

Intel MCS – Wikipedia

Views Read Edit View history. Where the least significant nibble of the opcode specifies one of the following addressing modes, the most significant specifies the operation:. These kinds of bit operations are notof the AT89C51 core is shown in Figure 1.

With one instruction, the can switch register banks versus the time consuming task of transferring the critical registers to the stack, or designated RAM locations. MOV bitC. JNZ offset jump if non-zero.

The absolute memory address is formed by the high 5 bits of the PC and the 11 bits defined by the instruction. Set when banks at 0x08 or 0x18 are in use. Bits are always specified by absolute addresses; there is no register-indirect or indexed addressing.

Enhancements mostly include new peripheral features and expanded arithmetic instructions. Allow the tester to assert. JNB bitoffset jump if bit clear. This specifies the address of the next instruction to execute.


Program memory is read-only, though some variants of the use on-chip flash memory and provide a method of re-programming the memory in-system or in-application. There is also a two-operand compare and jump operation. Design improvements have increased performance while retaining compatibility with the original MCS 51 instruction set. Se for the “.

Instruction Set

The on-chip Flash allows the program memory to be unstructionon a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible. They can not be accessed indirectly via R0 or R1; indirect access to those addresses will access the second half of IRAM.

Register select 0, RS0. Instruction mnemonics use destinationsource operand order.

The mnemonics for Accumulator-specific instructionshowever, refer to the Accumulator simply as Adivide operations. Intsruction following is a partial list of the ‘s registers, which are memory-mapped into the special function register space:. The original core ran at 12 clock cycles per machine cycle, with most instructions executing in one or two machine cycles.

ORL Adata. Innstruction discontinued its MCS product line in March ; [23] [24] however, there are plenty of enhanced products or silicon intellectual property added regularly from other vendors.