MSI Control Register @0x90
This register is used only when the Controller is configured to support Message Signaled Interrupts (MSIs). In addition to the MSI control bits, this location also contains the Capability ID for MSI and the pointer to the next PCI Capability Structure.
| Bits | SW | Name | Description | Reset |
|---|---|---|---|---|
| 7:0 | R | Capability ID [CID1] | Specifies that the capability structure is for MSI. Hardwired to 05 hex. | 0x05 |
| 15:8 | R | Capabilities Pointer [CP1] | Pointer to the next PCI Capability Structure. This can be modified from the local management bus. This field can be written from the local management bus. | 8'hb0 |
| 16 | R/W | MSI Enable [ME] | Set by the configuration program to enable the MSI feature. This field can also be written from the local management bus. | 0x0 |
| 19:17 | R | Multiple Message Capable [MMC] | Encodes the number of distinct messages that the Controller is capable of
generating for this Function (000 = 1, 001 = 2, 010 = 4, 011 = 8, 100 = 16, 101 = 32).
Thus, this field defines the number of the interrupt vectors for this Function. The
Controller allows up to 32 distinct messages, but the setting of this field must be
based on the number of interrupt inputs of the Controller that are actually used by
the client. For example, if the client logic uses 8 of the 32 distinct MSI
interrupt inputs of the Controller for this Function, then the value of this field
must be set to 011. This field can be written from the local management bus.
|
0x0 |
| 22:20 | R/W | Multiple Message Enable [MME] | Encodes the number of distinct messages that the Controller is programmed to generate for this Function (000 = 1, 001 = 2, 010 = 4, 011 = 8, 100 = 16, 101 = 32). This setting must be based on the number of interrupt inputs of the Controller that are actually used by this Function. This field can be written from the local management bus. | 0x0 |
| 23 | R | 64-Bit Address Capable [BAC64] | Set to 1 to indicate that the device is capable of generating 64-bit addresses for MSI messages. Can be modified using the local management interface | 0x1 |
| 24 | R | MSI masking capable [MC] | Can be modified using the local management interface. | 0x1 |
| 31:25 | R | Reserved [R0] | Reserved | 0x0 |