參數(shù)資料
型號(hào)： AM486DX2
廠商： Advanced Micro Devices, Inc.
英文描述： Am5X86⑩ Microprocessor Family
中文描述： Am5X86⑩微處理器家族
文件頁(yè)數(shù)： 46/67頁(yè)
文件大?。?/td> 1613K
代理商： AM486DX2
46
Am5
X
86 Microprocessor
AMD
PRELIMINARY
7.7.1
Exceptions and Interrupts with System
Management Mode
When the CPU enters SMM, it disables INTR interrupts,
debug, and single step traps by clearing the EFLAGS,
DR6, and DR7 registers. This prevents a debug appli-
cation from accidentally breaking into an SMI handler.
This is necessary because the SMI handler operates
from a distinct address space (SMRAM) and the debug
trap does not represent the normal system memory
space.
For an SMI handler to use the debug trap feature of the
processor to debug SMI handler code, it must first en-
sure that an SMM-compliant debug handler is available.
The SMI
handler must also ensure DR3–DR0 is saved
to be restored later. The debug registers DR3–DR0 and
DR7 must then be initialized with the appropriate values.
For the processor to use the single step feature of the
processor, it must ensure that an SMM-compliant single
step handler is available and then set the trap flag in the
EFLAGS register. If the system design requires the pro-
cessor to respond to hardware INTR requests while in
SMM, it must ensure that an SMM-compliant interrupt
handler is available, and then set the interrupt flag in the
EFLAGS register (using the STI instruction). Software
interrupts are not blocked on entry to SMM, and the
system software designer must provide an SMM-com-
pliant interrupt handler before attempting to execute any
software interrupt instructions. Note that in SMM mode,
the interrupt vector table has the same properties and
location as the Real mode vector table.
NMI interrupts are blocked on entry to the SMI handler.
If an NMI request occurs during the SMI handler, it is
latched and serviced after the processor exits SMM.
Only one NMI request is latched during the SMI handler.
If an NMI request is pending when the processor exe-
cutes the RSM instruction, the NMI is serviced before
the next instruction of the interrupted code sequence.
Although NMI requests are blocked when the CPU en-
ters SMM, they may be enabled through software by
executing an IRET instruction. If the SMI handler re-
quires the use of NMI interrupts, it should invoke a dum-
my interrupt service routine to execute an IRET
instruction. When an IRET instruction is executed, NMI
interrupt requests are serviced in the same Real mode
manner in which they are handled outside of SMM.
7.7.2
The 32-bit SMM Revision Identifier specifies the version
of SMM and the extensions that are available on the
processor. The fields of the SMM Revision Identifiers
and bit definitions are shown in Table 13 and Table 14.
Bit 17 or 16 indicates whether the feature is supported
(1=supported, 0=not supported). The processor always
reads the SMM Revision Identifier at the time of a re-
store. The I/O Trap Extension and SMM Base Reloca-
tion bits are fixed. The processor writes these bits out
at the time it performs a save state.
SMM Revisions Identifier
Note:
Changing the state of the reserved bits may result
in unpredictable processor behavior.
Table 13. SMM Revision Identifier
31–18
17
16
15–0
Reserved
SMM Base
Relocation
1
I/O Trap
Extension
1
SMM Revision Level
00000000000000
0000h
Table 14. SMM Revision Identifier Bit Definitions
Bit Name
Description
Default
State
State at
SMM
Entry
State at
SMM Exit
Notes
SMM Base
Relocation
1=SMM Base Relocation Available
0=SMM Base Relocation
Unavailable
1
1
0
1
0
No Change in State
No Change in State
I/O Trap Extension
1=I/O Trapping Available
0=I/O Trapping Unavailable
1
1
0
1
0
No Change in State
No Change in State
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AM486DX2-66V16BGC 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 66MHz 5V 168-Pin PGA
AM486DX2-66V16BGI 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 66MHz 5V 168-Pin PGA
AM486DX2-66V16BHI 制造商:Advanced Micro Devices 功能描述:MPU AM486 RISC 32-Bit 0.35um 66MHz 5V 208-Pin SQFP
AM486DX4100C16BGI 制造商:AMD 功能描述:*
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