The following pages describe the 8051 instruction set.
Instructions are listed in alphabetical order and each is divided
into several sections:
Description
Describes the instruction's effect and
describes any arguments.
See Also
Names related instructions.
Bytes
Lists the number of bytes required to encode
the instruction.
Cycles
Lists the number of instruction cycles
required to execute the instruction. Note that there are 12
oscillator cycles to one instruction cycle on a standard
8051.
Encoding
Lists the byte encoding for the
instruction.
Operation
Lists, step-by-step, the operations
performed by the instruction.
Example
Shows proper use of the instruction.
Many instructions have required arguments that are described in
the following table:
Argument
Description
addr11
An 11-bit address destination. This argument is
used by ACALL and AJMP instructions. The target of the
CALL or JMP must lie within the same 2K page as the first byte
of the following instruction.
addr16
A 16-bit address destination. This argument is
used by LCALL and LJMP instructions.
bit
A direct addressed bit in internal data RAM or
SFR memory.
direct
An internal data RAM location (0-127) or SFR
(128-255).
immediate
A constant included in the instruction
encoding.
offset
A signed (two's complement) 8-bit offset (-128
to 127) relative to the first byte of the following
instruction.
@Ri
An internal data RAM location (0-255) addressed
indirectly through R0 or R1.
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