Vol. 3A 10-35
ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (APIC)
each local APIC. The details are similar to those described in Section 10.6.2, “Determining IPI Destination.” If
RH is 0, then the DM bit is ignored and the message is sent ahead independent of whether the physical or
logical destination mode is used.
10.11.2 Message Data Register Format
The layout of the Message Data Register is shown in Figure 10-25.
Reserved fields are not assumed to be any value. Software must preserve their contents on writes. Other fields in
the Message Data Register are described below.
1. Vector — This 8-bit field contains the interrupt vector associated with the message. Values range from 010H
to 0FEH. Software must guarantee that the field is not programmed with vector 00H to 0FH.
2. Delivery Mode — This 3-bit field specifies how the interrupt receipt is handled. Delivery Modes operate only in
conjunction with specified Trigger Modes. Correct Trigger Modes must be guaranteed by software. Restrictions
are indicated below:
a. 000B (Fixed Mode) — Deliver the signal to all the agents listed in the destination. The Trigger Mode for
fixed delivery mode can be edge or level.
b. 001B (Lowest Priority) — Deliver the signal to the agent that is executing at the lowest priority of all
agents listed in the destination field. The trigger mode can be edge or level.
c. 010B (System Management Interrupt or SMI) — The delivery mode is edge only. For systems that rely
on SMI semantics, the vector field is ignored but must be programmed to all zeroes for future compatibility.
d. 100B (NMI) — Deliver the signal to all the agents listed in the destination field. The vector information is
ignored. NMI is an edge triggered interrupt regardless of the Trigger Mode Setting.
e. 101B (INIT) — Deliver this signal to all the agents listed in the destination field. The vector information is
ignored. INIT is an edge triggered interrupt regardless of the Trigger Mode Setting.
Figure 10-25. Layout of the MSI Message Data Register
Reserved
Reserved
Reserved
Vector
Delivery Mode
001 - Lowest Priority
010 - SMI
011 - Reserved
101 - INIT
110 - Reserved
111 - ExtINT
Trigger Mode
0 - Edge
1 - Level
Level for Trigger Mode = 0
X - Don’t care
Level for Trigger Mode = 1
0 - Deassert
1 - Assert
000 - Fixed
100 - NMI
31
16
15
14
13
11 10
8
7
0
63
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