
Instruction Set Overview
2-1
CHAPTER
2
INSTRUCTION SET OVERVIEW
2.1
OVERVIEW
The instruction set used by the Am186 and Am188 family of microcontrollers is identical to
the original 8086 and 8088 instruction set, with the addition of seven instructions (BOUND,
ENTER, INS, LEAVE, OUTS, POPA, and PUSHA), and the enhancement of nine
instructions (immediate operands were added to IMUL, PUSH, RCL, RCR, ROL, ROR,
SAL/SHL, SAR, and SHR). In addition, three valid instructions are not supported with the
necessary processor pinout (ESC, LOCK and WAIT). All of these instructions are marked
as such in their description.
2.2
INSTRUCTION FORMAT
When assembling code, an assembler replaces each instruction statement with its
machine-language equivalent. In machine language, all instructions conform to one basic
format. However, the length of an instruction in machine language varies depending on the
operands used in the instruction and the operation that the instruction performs.
An instruction can reference from zero to several operands. An operand can reside in a
register, in the instruction itself, or in memory.
The Am186 and Am188 microcontrollers use the following instruction format. The shortest
instructions consist of only a single opcode byte.
2.2.1
Instruction Prefixes
The REP, REPE, REPZ, REPNE and REPNZ prefixes can be used to repeatedly execute
a single string instruction.
The LOCK prefix may be combined with the instruction and segment override prefixes, and
causes the processor to assert its bus LOCK signal while the instruction that follows
executes.
Instruction Prefixes
Segment Override Prefix
Opcode
Operand Address
Displacement
Immediate
Содержание Am186 Series
Страница 1: ...Am186 and Am188 Family Instruction Set Manual February 1997...
Страница 10: ...Table of Contents x...
Страница 18: ...Programming 1 8...
Страница 40: ...Instruction Set Listing 3 14...