Intel
®
81341 and 81342—Messaging Unit
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
452
Order Number: 315037-002US
4.9.32
Message Control Register - Message_Control
The Message Control Register provides system software control over MSI. After reset,
MSI is disabled. System software is permitted to modify the Message Control register’s
read/write bits and fields while a device driver is not permitted to modify them.
Note:
Refer to the Peripheral Registers Chapter for the default internal bus address. This
register is part of the configuration space of the Address Translation Unit that is setup
as an endpoint.
Table 296. Message Control Register - Message_Control
Bit
Default
Description
15:8
00H
Reserved
7
1
2
64-bit Address Support - This field is set to 1
2
indicating that the 81341 and 81342
is capable of
generating a 64-bit message address.
6:4
000
2
Multiple Message Enable - System software writes to this field to indicate the number of messages
allocated to the 81341 and 81342. While, the 81341 and 81342
requests two messages, it is possible
that system software only allocates one message. The device hardware is designed to handle both
cases.
3:1
001
2
Multiple Message Capable - This field is set to 001
2
indicating that the 81341 and 81342
can issue up to
two unique interrupt messages.
0
0
2
MSI Enable - Setting this bit enables the 81341 and 81342’s MSI functionality and disables the use of
the
P_INTA#
interrupt output for 81341 and 81342
interrupts
.
PCI
IOP
Attributes
Attributes
15
12
8
4
0
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
rv
ro
ro
rw
rw
rw
rw
rw
rw
ro
ro
ro
ro
ro
ro
rw
rw
Attribute Legend:
RV = Reserved
PR = Preserved
RS = Read/Set
RW = Read/Write
RC = Read Clear
RO = Read Only
NA = Not Accessible
PCI Configuration Offset
A2H
Internal Bus Address Offset
0A2H