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Processor Programming (Continued)

3.11.9.2 CPU States Related to SMM and Suspend

Mode

The state diagram shown in Figure 3-12 illustrates the var-

ious CPU states associated with SMM and Suspend

mode. While in the SMI service routine, the GXm proces-

sor core can enter Suspend mode either by (1) executing

a halt (HLT) instruction or (2) by asserting the SUSP#

input.

During SMM operations and while in SUSP#-initiated

Suspend mode, an occurrence of either NMI or INTR is

latched. (In order for INTR to be latched, the IF flag,

EFLAGS register bit 9, must be set.) The INTR or NMI is

serviced after exiting Suspend mode.

If Suspend mode is entered through a HLT instruction

from the operating system or application software, the

reception of an SMI# interrupt causes the CPU to exit

Suspend mode and enter SMM. If Suspend mode is

entered through the hardware (SUSP# = 0) while the

operating system or application software is active, the

CPU latches one occurrence of INTR, NMI, and SMI#.

Figure 3-12. SMM and Suspend Mode State Diagram

Suspend Mode

(SUSPA# = 0)

Suspend Mode

(SUSPA# = 0)

Suspend Mode

(SUSPA# = 0)

NMI or INTR

HLT*

IRET*

RSM*

SMI# = 0

SMINT*

SUSP# = 1

SUSP# = 0

Interrupt Service

Routine

Interrupt Service

Routine

OS/Application

Software

SMI Service Routine

(SMI# = 0)

NMI or INTR

RESET

SMI# = 0

(INTR, NMI and SMI# latched)

Non-SMM Operations

SMM Operations

Interrupt Service

Routine

Suspend Mode

(SUSPA# = 0)

(INTR and NMI latched)

NMI or INTR

IRET*

SUSP# = 0

SUSP# = 1

IRET*

HLT*

NMI or INTR

*Instructions

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