AN 763: Intel® Arria® 10 SoC Device Design Guidelines

ID 683192
Date 5/17/2022
Public
Document Table of Contents

4.5.3. QSPI Flash Interface Design Guidelines

GUIDELINE: Ensure that the QSPI_SS signals are used in numerical order.

Up to four QSPI chip selects can be used with Intel® Arria® 10 SoCs. The device can boot only from QSPI connected to the chip select zero.

Intel® Quartus® Prime assumes that the QSPI_SS signals are used in order. It is not possible to use SS0 and SS2, for example, without using SS1.

Note: The QSPI_SS1 pin is also used as BSEL0. Therefore, when selecting BSEL=0x6 (1.8V QSPI), the QSPI_SS1 cannot be directly connected to QSPI chip select.

As the HPS BSEL values are sampled upon deassertion of cold reset, it is necessary to decouple the QSPI_SS1 pin from QSPI chip select to ensure the QSPI is not enabled while the HPS is under reset condition.

This can be achieved through, for example, an external buffer in conjunction with proper external pull up on the QSPI Flash side.

Once the HPS exits the cold reset stage, the QSPI_SS1 pin is driven correctly by the HPS according to the transaction and hence the buffer can become always enabled.

There are no restriction if you use 3.3V QSPI, instead.

For more information about supported QSPI devices, refer to the "Supported Flash Devices for Intel® Arria® 10 SoCs" web page on the Intel FPGA Support website.

For more information about booting from the QSPI flash, refer to the "Booting from QSPI Flash" web page on the RocketBoards.org website.

For more information about programming the QSPI flash, refer to the "Programming QSPI Flash" web page on the RocketBoards.org website.

GUIDELINE: If a QSPI flash with 4-byte addressing is used, design the board to ensure that the QSPI flash is reset or power-cycled whenever the HPS is reset.

The Intel® Arria® 10 HPS Boot ROM is designed to work with the 3-byte address mode default setting. If the QSPI flash has been switched to 4-byte addressing during operation, you need to ensure that it is returned to its default 3-byte addressing mode whenever the HPS is reset. Otherwise, the HPS is not able to boot from or access the QSPI chip.

Methods to switch the QSPI back to default 3-byte addressing mode are:
  • For QSPI device with reset pin, assert the reset signal every time the HPS device is reset
  • For QSPI device without reset pin, power cycle the QSPI chip every time the HPS device is reset

The Intel® Arria® 10 SoC Development Kit uses a reset scheme that ensures the QSPI flash is being reset whenever the HPS undergoes reset.