GTS AXI Multichannel DMA IP for PCI Express* User Guide
C.2. MSI-X Memory Space
The MSI-X Table and Pending Bit Array (PBA) memory are mapped to the second MB space of the register address space. The actual amount of memory depends on the GTS AXI MCDMA IP configuration.
MSI-X Table
Each entry (vector) is 16 bytes (4 DWORDs) and is divided into Message Address, Data, and Mask (Vector Control) fields as shown in the figure below. Though the actual required space is smaller, the MSI-X Table is mapped to a 512 KB of space.
MSI-X PBA
The MSI-X PBA memory space is mapped to a 512 KB region. The actual amount of memory depends on the IP configuration. The Pending Bit Array contains the Pending bits, one per MSI-X Table entry, in an array of QWORDs (64 bits). The PBA format is shown below.
Each DMA Channel is allocated 4 MSI-X vectors:
- 2’b00: H2D DMA Vector
- 2’b01: H2D Event Interrupt
- 2’b10: D2H DMA Vector
- 2’b11: D2H Event Interrupt