Altera Arria V Avalon-MM - Manual (Page 128)

PCI Express-to-Avalon-MM Read Completions
The PCI Express Avalon-MM bridge returns read completion packets to the initiating Avalon-MM
master in the issuing order. The bridge supports multiple and out-of-order completion packets.
PCI Express-to-Avalon-MM Downstream Write Requests
The PCI Express Avalon-MM bridge receives PCI Express write requests, it converts them to burst write
requests before sending them to the interconnect fabric. For Endpoints, the bridge translates the PCI
Express address to the Avalon-MM address space based on the BAR hit information and on address
translation table values configured during the IP core parameterization. For Root Ports, all requests are
forwarded to a single RX Avalon-MM master that drives them to the interconnect fabric. Malformed write
packets are dropped, and therefore do not appear on the Avalon-MM interface.
For downstream write and read requests, if more than one byte enable is asserted, the byte lanes must be
adjacent. In addition, the byte enables must be aligned to the size of the read or write request.
As an example, the following table lists the byte enables for 32-bit data.
Table 9-2: Valid Byte Enable Configurations
Byte Enable Value Description
4’b1111 Write full 32 bits
4’b0011 Write the lower 2 bytes
4’b1100 Write the upper 2 bytes
4’b0001 Write byte 0 only
4’b0010 Write byte 1 only
4’b0100 Write byte 2 only
4’b1000 Write byte 3 only
In burst mode, the Arria V Hard IP for PCI Express supports only byte enable values that correspond to a
contiguous data burst. For the 32-bit data width example, valid values in the first data phase are 4’b1111,
4’b1110, 4’b1100, and 4’b1000, and valid values in the final data phase of the burst are 4’b1111, 4’b0111,
4’b0011, and 4’b0001. Intermediate data phases in the burst can only have byte enable value 4’b1111.
PCI Express-to-Avalon-MM Downstream Read Requests
The PCI Express Avalon-MM bridge sends PCI Express read packets to the interconnect fabric as burst
reads with a maximum burst size of 512 bytes. For Endpoints, the bridge converts the PCI Express address
to the Avalon-MM address space based on the BAR hit information and address translation lookup table
values. The RX Avalon-MM master port drives the received address to the fabric. You can set up the
Address Translation Table Configuration in the parameter editor. Unsupported read requests generate a
completer abort response.
9-12 PCI Express-to-Avalon-MM Read Completions
UG-01105_avmm
2014.12.15
Altera Corporation IP Core Architecture
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