Visible to Intel only — GUID: sfo1410068133723
Ixiasoft
Visible to Intel only — GUID: sfo1410068133723
Ixiasoft
9.3.3. Functional Description of the HPS-to-FPGA Bridge
The HPS-to-FPGA bridge provides a configurable-width, high-performance master interface to the FPGA fabric. The bridge provides most masters in the HPS with access to logic, peripherals, and memory implemented in the FPGA. The effective size of the address space is 0x3FFF0000, or 1 gigabyte (GB) minus the 64 megabytes (MB) occupied by peripherals, lightweight HPS-to-FPGA bridge, on-chip RAM, and boot ROM in the HPS. You can configure the bridge master exposed to the FPGA fabric for 32-, 64-, or 128-bit data. The amount of address space exposed to the MPU subsystem can also be reduced through the L2 cache address filtering mechanism.
The slave interface of the bridge in the HPS logic has a data width of 64 bits. The bridge provides width adaptation and clock crossing logic that allows the logic in the FPGA to operate in any clock domain, asynchronous from the HPS.
Bridge Property | L3 Slave Interface | FPGA Master Interface |
---|---|---|
Data width 20 |
64 bits |
32, 64, or 128 bits |
Clock domain |
l3_main_clk | h2f_axi_clk |
Byte address width |
32 bits |
30 bits |
ID width |
12 bits |
12 bits |
Read acceptance |
16 transactions |
16 transactions |
Write acceptance |
16 transactions |
16 transactions |
Total acceptance |
32 transactions |
32 transactions |
The HPS-to-FPGA bridge’s GPV, described in "The Global Programmers View", provides settings to adjust the bridge master properties. The master issuing capability can be adjusted, through the fn_mod register, to allow one or multiple transactions to be outstanding in the FPGA fabric. The master bypass merge feature can also be enabled, through the bypass_merge bit in the fn_mod2 register. This feature ensures that the upsizing and downsizing logic does not alter any transactions when the FPGA master interface is configured to be 32 or 128 bits wide.