User's Manual

Vol. 3 9-33

PROCESSOR MANAGEMENT AND INITIALIZATION

9.10.3 MAIN.ASM Source Code

The file MAIN.ASM shown in Example 9-2 defines the data and stack segments for

this application and can be substituted with the main module task written in a high-

level language that is invoked by the IRET instruction executed by STARTUP.ASM.

Example 9-2. MAIN.ASM

NAME main_module

data SEGMENT RW

dw 1000 dup(?)

DATA ENDS

stack stackseg 800

Figure 9-6. Task Switching (Lines 282-296 of List File)

GDT RAM

RAM_START

TSS RAM

IDT RAM

GDT Alias

IDT Alias

EIP

EFLAGS

ESP

•

SS = TSS.SS

ESP = TSS.ESP

PUSH TSS.EFLAG

PUSH TSS.CS

PUSH TSS.EIP

ES = TSS.ES

DS = TSS.DS

IRET

GDT