Intel® Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 4/02/2022
Public

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7.1.8.4. Using the Address Span Extender

This example shows when and how to use address span extender component in your Platform Designer design.

Figure 218. Block Diagram with Address Span Extender

In the above design, a 32-bit host shares 4 GB SDRAM with an external streaming interface. The host has the path to access streaming data from the SDRAM DDR memory. However, if you connect the whole 32-bit address bus of the host to the SDRAM DDR memory, you cannot connect the host to peripherals such as LED or UART. To avoid this situation, you can implement the address span extender between the host and DDR memory. The address span extender allows the host to access the SDRAM DDR memory and the peripherals at the same time.

To implement address span extender for the above example, you can divide the address window of the address span extender into two sub-windows of 512 MB each. The sub-window 0 is for the host program area. You can dynamically map the sub-window 1 to any area other than the program area.

You can change the offset of the address window by setting the base address of sub-window 1 to the control register of the address span extender. However, you must make sure that the sub-window address span masks the base address. You can choose any arbitrary base address. If you set the value 0xa000_0000 to the control register, Platform Designer maps the sub-window 1 to 0xa000_0000.

Table 126.  CSR Mapping Table
Address Data

0x8000_0000

0x0000_0000

0x8000_0008

0xa000_0000

Figure 219. Memory mapping for Address Span Extender

The table below indicates the Platform Designer parameter settings for this address span extender example.

Table 127.  Parameter Settings for the Address Span Extender Example
Parameter Value Description

Datapath Width

32 bits

The CPU has 32-bits data width and the SDRAM DDR memory has 512-bits data width. Since the transaction between the host and SDRAM DDR memory is minimal, set the datapath width to align with the upstream host.

Expanded Master Byte Address

32 bits

The address span extender has a 4 GB address span.

Slave Word Address Width

18 bits

There are two 512 MB sub-windows in reserve for the host. The number of bytes over the data word width in the Datapath Properties (4 bytes for this example) accounts for the agent address.

Burstcount Width

4 bits

The address span extender must handle up to 8 words burst in this example.

Number of sub-windows

2

Address window of the address span extender has two sub-windows of 512 MB each.

Enable Slave Control Port

true

The address span extender component must have control to change the base address of the sub-window.

Maximum Pending Reads

4

This number is the same as SDRAM DDR memory burst count.

Figure 220. Address Span Extender Parameter Editor
Note: You can view the address span extender connections in the System View tab. The windowed agent port and control port connect to the host. The expanded host port connects to the SDRAM DDR memory.