Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
423
Messaging Unit—Intel
®
81341 and 81342
To signal an Outbound Interrupt with MSI-X enabled, the 81341 and 81342 creates an
outbound write transaction using the Message Address and the Message Data of the
associated entry. On 81341 and 81342, entry 0 of the MSI-X Table is assigned to bit
OISR[0], entry 1 is assigned to bit OISR[1] and so on. For example, entry 7 of the MSI-
X Table is assigned to bit OISR[7].
Note:
Entry 2 is assigned to bits OSIR[2] and OISR[31]. For example, the Outbound Doorbell
Register and the Firmware Interrupt bit in the Outbound Control and Status Register.
Note:
When host software enables MSI, a Messaging Unit Interrupt does not result in the
assertion of the
P_INTx#
output pin. However, all the
P_INT[A:D]#
pins are
functional for steering of interrupts from other PCI devices that may not be MSI
capable.
MSI-X Table and Pending Bits Array are mapped relative to the PCI/Host interface
(
). The MU registers are located in the first 4-KByte of the 8-KByte address
space claimed by the MU, whereas the MSI-X Table is located at a 4-KByte offset and
the MSI-X PBA is located at a 6-KByte offset relative to the MU Base Address. Note that
the MU Base Address register must be programmed such that it overlaps the address
space defined by the ATU Translate and ATU Limit Registers. For example, the MU 8-
KByte window must overlap onto the ATU Translation Window.
Figure 45. MSI-X Table and PBA Address Mapping Layout relative to the Host Interface
MU Registers
8 KBytes
MU BAR
4 KB
MSI-X PBA
MSI-X Table
4 KB
2 KB
2 KB
NOTE: MU space must overlap the ATU Translation Window.
B6216-01