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
64 megabytes (MB). The address space size is less than 1 GB because 64 MB is 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.
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.
Note:
The following table lists the properties of the HPS-to-FPGA bridge, including the configurable master
interface exposed to the FPGA fabric.
Table 5-9: HPS-to-FPGA Bridge Properties
FPGA Master Interface
L3 Slave Interface
Bridge Property
32, 64, or 128 bits
64 bits
Data width
(3)
h2f_axi_clk
l3_main_clk
Clock domain
30 bits
32 bits
Byte address width
12 bits
12 bits
ID width
16 transactions
16 transactions
Read acceptance
16 transactions
16 transactions
Write acceptance
32 transactions
32 transactions
Total acceptance
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.
It is critical to provide the correct
l4_mp_clk
clock to support access to the GPV, as described in
GPV Clocks
.
Note:
(3)
The bridge master data width is user-configurable at the time you instantiate the HPS component in your
system.
Altera Corporation
HPS-FPGA AXI Bridges
5-7
HPS-to-FPGA Bridge
cv_54005
2013.12.30