Intel IA-32 - Manual (Page 370)

8-46 Vol. 3A
ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (APIC)
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.
Figure 8-25. 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
001 - NMI
31 16 15 14 13 11 10 8 7 0
63 32