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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
DS
EIP
EFLAGS
CS
SS
0
ES
ESP
•
•
•
•
•
•
SS = TSS.SS
ESP = TSS.ESP
PUSH TSS.EFLAG
PUSH TSS.CS
PUSH TSS.EIP
ES = TSS.ES
DS = TSS.DS
IRET
GDT