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OVERVIEW OF THE 80C186 FAMILY ARCHITECTURE
2-6
Figure 2-4. Segment Registers
2.1.5 Instruction 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).
15 0
CS Code Segment
DS Data Segment
SS Stack Segment
ES Extra Segment