Intel 80C186XL, 80C188XL 2.1.5Instruction Pointer, OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE

Models: 80C186XL 80C188XL

1 405
Download 405 pages 42.62 Kb
Page 35
Image 35
Figure 2-4. Segment Registers

OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE

15

0

CS

DS

SS

ES

Code Segment

Data Segment

Stack Segment

Extra Segment

Figure 2-4. Segment Registers

2.1.5Instruction Pointer

The Bus Interface Unit updates the 16-bit Instruction Pointer (IP) register so it contains the offset of the next instruction to be fetched. Programs do not have direct access to the Instruction Pointer, but it can change, be saved or be restored as a result of program execution. For example, if the Instruction Pointer is saved on the stack, it is first automatically adjusted to point to the next in- struction to be executed.

Reset initializes the Instruction Pointer to 0000H. The CS and IP values comprise a starting exe- cution address of 0FFFF0H (see “Logical Addresses” on page 2-10 for a description of address formation).

2-6

Page 35
Image 35
Intel 80C186XL, 80C188XL 2.1.5Instruction Pointer, OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE, 4.Segment Registers