Please refer to the following sample for implementation.
SPI Slave to Avalon Master Bridge Design Example
https://www.intel.com/content/www/us/en/programmable/support/support-resources/design- examples/intellectual-property/embedded/nios-ii/exm-spi-bridge.html?elq_cid=5331786_ts1605579456607&erpm_id=8281062_ts 1605579456607
Please refer to the following document for protocol details.
(Reference) Embedded Peripherals IP User Guide
https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/ug_embedded_ip.pdf
(6) SPI Slave/JTAG to Avalon Master Bridge Cores)
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Category: Quartus® Prime (Platform Designer)
Tools: Quartus® Prime
Devices: -