AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 23

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

2.1
CHAPTER
2
PROGRAMMING
All members of the Am186 and Am188 family of microcontrollers, including the Am186ES
and Am188ES, contain the same basic set of registers, instructions, and addressing modes,
and are compatible with the original industry-standard 186/188 parts.
REGISTER SET
The base architecture of the Am186ES and Am188ES microcontrollers has 14 registers,
as shown in Figure 2-1. These registers are grouped into the following categories.
Note that the Am186ES and Am188ES microcontrollers have additional peripheral
registers, which are external to the processor. These external registers are not accessible
by the instruction set. However, because the processor treats these peripheral registers
like memory, instructions that have operands that access memory can also access
peripheral registers. The above processor registers, as well as the additional peripheral
registers, are described in the chapters that follow.
General Registers—Eight 16-bit genera-purpose registers can be used for arithmetic
and logical operands. Four of these (AX, BX, CX, and DX) can be used as 16-bit registers
or split into pairs of separate 8-bit registers (AH, AL, BH, BL, CH, CL, DH, and DL). The
Destination Index (DI) and Source Index (SI) general-purpose registers are used for
data movement and string instructions. The Base Pointer (BP) and Stack Pointer (SP)
general-purpose registers are used for the stack segment and point to the bottom and
top of the stack, respectively.
— Base and Index Registers—Four of the general-purpose registers (BP, BX, DI, and
— Stack Pointer Register—All stack operations (POP, POPA, POPF, PUSH, PUSHA,
Segment Registers—Four 16-bit special-purpose registers (CS, DS, ES, and SS)
select, at any given time, the segments of memory that are immediately addressable
for code (CS), data (DS and ES), and stack (SS) memory. (For usage, refer to section
2.2.)
Status and Control Registers—Two 16-bit special-purpose registers record or alter
certain aspects of the processor state—the Instruction Pointer (IP) register contains the
offset address of the next sequential instruction to be executed and the Processor Status
Flags (FLAGS) register contains status and control flag bits (see Figure 2-1 and Figure
2-2).
SI) can also be used to determine offset addresses of operands in memory. These
registers can contain base addresses or indexes to particular locations within a
segment. The addressing mode selects the specific registers for operand and address
calculations.
PUSHF) utilize the stack pointer. The Stack Pointer register is always offset from the
Stack Segment (SS) register, and no segment override is allowed.
Programming
2-1