Cyclone® V Hard Processor System Technical Reference Manual

ID 683126
Date 8/28/2023
Public
Document Table of Contents

28.5. Using the Address Span Extender Component

The FPGA-to-HPS bridge and FPGA-to-HPS SDRAM memory-mapped interfaces expose their entire 4-GB address spaces to the FPGA fabric. The address span extender component provides a memory-mapped window into the address space that it masters. Using the address span extender, you can expose portions of the HPS memory space without needing to expose the entire 4 GB address space.

You can use the address span extender between a soft logic master and an FPGA-to-HPS bridge or FPGA-to-HPS SDRAM interface. This component reduces the number of address bits required for a master to address a memory-mapped slave interface located in the HPS.

Figure 141. Address Span Extender Components Two address span extender components used in a system with the HPS.

You can also use the address span extender in the HPS-to-FPGA direction, for slave interfaces in the FPGA. In this case, the HPS-to-FPGA bridge exposes a limited, variable address space in the FPGA, which can be paged in using the address span extender.

For example, suppose that the HPS-to-FPGA bridge has a 1-GB span, and the HPS needs to access three independent 1-GB memories in the FPGA portion of the device. To achieve this, the HPS programs the address span extender to access one SDRAM (1-GB) in the FPGA at a time. This technique is commonly called paging or windowing.