Intel 253668-032US Benutzerhandbuch
9-22 Vol. 3
PROCESSOR MANAGEMENT AND INITIALIZATION
9.10.1 Assembler
Usage
In this example, the Intel assembler ASM386 and build tools BLD386 are used to
assemble and build the initialization code module. The following assumptions are
used when using the Intel ASM386 and BLD386 tools.
assemble and build the initialization code module. The following assumptions are
used when using the Intel ASM386 and BLD386 tools.
•
The ASM386 will generate the right operand size opcodes according to the code-
segment attribute. The attribute is assigned either by the ASM386 invocation
controls or in the code-segment definition.
segment attribute. The attribute is assigned either by the ASM386 invocation
controls or in the code-segment definition.
•
If a code segment that is going to run in real-address mode is defined, it must be
set to a USE 16 attribute. If a 32-bit operand is used in an instruction in this code
segment (for example, MOV EAX, EBX), the assembler automatically generates
an operand prefix for the instruction that forces the processor to execute a 32-bit
operation, even though its default code-segment attribute is 16-bit.
set to a USE 16 attribute. If a 32-bit operand is used in an instruction in this code
segment (for example, MOV EAX, EBX), the assembler automatically generates
an operand prefix for the instruction that forces the processor to execute a 32-bit
operation, even though its default code-segment attribute is 16-bit.
•
Intel's ASM386 assembler allows specific use of the 16- or 32-bit instructions, for
example, LGDTW, LGDTD, IRETD. If the generic instruction LGDT is used, the
default- segment attribute will be used to generate the right opcode.
example, LGDTW, LGDTD, IRETD. If the generic instruction LGDT is used, the
default- segment attribute will be used to generate the right opcode.
188
195
Perform specific board initialization that is imposed by the new
protected mode
196
218
Copy the application's GDT from ROM into RAM
220
238
Copy the application's IDT from ROM into RAM
241
243
Load application's GDTR
244
245
Load application's IDTR
247
261
Copy the application's TSS from ROM into RAM
263
267
Update TSS descriptor and other aliases in GDT (GDT alias or IDT
alias)
277
277
Load the task register (without task switch) using LTR instruction
282
286
Load SS, ESP with the value found in the application's TSS
287
287
Push EFLAGS value found in the application's TSS
288
288
Push CS value found in the application's TSS
289
289
Push EIP value found in the application's TSS
290
293
Load DS, ES with the value found in the application's TSS
296
296
Perform IRET; pop the above values and enter the application code
Table 9-4. Main Initialization Steps in STARTUP.ASM Source Listing (Contd.)
STARTUP.ASM Line
Numbers
Description
From
To