
Chapter 5: IP Core Interfaces 5–9
Avalon-ST Interface
August 2014 Altera Corporation IP Compiler for PCI Express User Guide
Table 5–3 shows the byte ordering for header and data packets for Figure 5–5 through
Figure 5–13.
Figure 5–5 illustrates the mapping of Avalon-ST RX packets to PCI Express TLPs for a
three dword header with non-qword aligned addresses with a 64-bit bus. In this
example, the byte address is unaligned and ends with 0x4, causing the first data to
correspond to
rx_st_data[63:32]
.
f For more information about the Avalon-ST protocol, refer to the Avalon Interface
Specifications.
1 The Avalon-ST protocol, as defined in Avalon Interface Specifications, is big endian, but
the IP Compiler for PCI Express packs symbols into words in little endian format.
Consequently, you cannot use the standard data format adapters that use the Avalon-
ST interface.
Table 5–3. Mapping Avalon-ST Packets to PCI Express TLPs
Packet TLP
Header0 pcie_hdr_byte0, pcie_hdr _byte1, pcie_hdr _byte2, pcie_hdr _byte3
Header1 pcie_hdr _byte4, pcie_hdr _byte5, pcie_hdr byte6, pcie_hdr _byte7
Header2 pcie_hdr _byte8, pcie_hdr _byte9, pcie_hdr _byte10, pcie_hdr _byte11
Header3 pcie_hdr _byte12, pcie_hdr _byte13, header_byte14, pcie_hdr _byte15
Data0 pcie_data_byte3, pcie_data_byte2, pcie_data_byte1, pcie_data_byte0
Data1 pcie_data_byte7, pcie_data_byte6, pcie_data_byte5, pcie_data_byte4
Data2 pcie_data_byte11, pcie_data_byte10, pcie_data_byte9, pcie_data_byte8
Data<n> pcie_data_byte<n>, pcie_data_byte<n-1>, pcie_data_byte<n>-2, pcie_data_byte<n-3>
Figure 5–5. 64-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-DWord Header TLPs with Non-QWord Aligned Address
clk
rx_st_data[63:32]
rx_st_data[31:0]
rx_st_sop
rx_st_eop
rx_st_be[7:4]
rx_st_be[3:0]
Header1 Data0 Data2
Header0 Header2 Data1
F F
F
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