Arria V Hard Processor System Technical Reference Manual

ID 683011
Date 12/02/2022
Public
Document Table of Contents

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.

Note: The HPS-to-FPGA bridge is accessed if the MPU boots from the FPGA. Before the MPU boots from the FPGA, the FPGA portion of the SoC device must be configured, and the HPS-to-FPGA bridge must be remapped into addressable space.
Table 44.  HPS-to-FPGA Bridge PropertiesThe following table lists the properties of the HPS-to-FPGA bridge, including the configurable master interface exposed to the FPGA fabric.
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.

Note: It is critical to provide the correct l4_mp_clk clock to support access to the GPV, as described in "GPV Clocks".
20 The bridge master data width is user-configurable at the time you instantiate the HPS component in your system.