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Bare-Metal Application Boot from Flash on the Xilinx Zynq-7000 of the ZC702

Updated: May 14, 2023


This post lists how to create a complete bare-metal application that boots from the Micron Quad SPI and what happens during boot.


The ZC702 Rev 1.1 board [schematic][user guide] has a XC7Z020CLG484 Zynq-7000 [TRM] which can boot from a N25Q128A (Micron Serial NOR Flash Memory 1.8V, Multiple I/O, 4KB Sector Erase) Quad SPI [datasheet].


Note: AR# 50991 Zynq-7000 SoC - What devices are supported for configuration? at [link] covers this and the other flash devices supported by the Zynq-7000:


Note 2: 2016.4 was used to create this write up.


Build the FSBL and an App


1. Run Xilinx SDK 2016.4


2. Create a workspace called FSBLandAppDemo


3. Select File > New > Application Project


Use Project name: DemoFSBL


...and the following settings and click Next:


4. Select Zynq FSBL and click Finish


5. Again, select File > New > Application Project


Use Project name: HelloWorld

Select Use existing DemoFSBL_bsp


...and the following settings and click Next:


6. Leave Hello World selected and click Finish


7. Select Project > Build All


8. Select Xilinx Tools > Create Boot Image


Set Output BIF file path to C:\Users\pfefferz\FSBLandAppDemo_out\DemoFSBL.bif


Set Output path to C:\Users\pfefferz\FSBLandAppDemo_out\BOOT.bin


Click Add


Find C:\Users\pfefferz\FSBLandAppDemo\DemoFSBL\Debug\DemoFSBL.elf

Set Partition type to bootloader

Click OK


Click Add


Find C:\Users\pfefferz\FSBLandAppDemo\Helloworld\Debug\HelloWorld.elf

Set Partition type to datafile

Click OK


Click Create Image


9. Click Xilinx Tools > Program Flash


10. Plug the USB UART and USB JTAG Cables in


11. Set the window as follows and click Program


You should see:



Background


1. Power is applied to the Zynq-7000 and the first instruction of the BootROM is executed at 0x0 (the BootROM cannot be changed).


2. The BootROM reads the boot-mode pins (via the Boot Mode Register) to figure out which device holds the first stage boot loader (FSBL) it should load via the memory controller to the OCM to run. It also initializes essential clocks and the device that holds the next code to run.


For the ZC702 to boot from Quad SPI SW16 should be set to:

...which corresponds to the following physical switch settings


3. The BootROM reads the BootROM Header and performs two checks to verify that the header is valid. It looks to see that the Image Identification parameter contains 0x584C4E58 ( XLNX at 0x024) and that the Header Checksum parameter (0x048) matches the checksum calculated by the BootROM. If either of these tests fail, then the BootROM Header address increments by 32 KB and the tests are repeated.


Note:


The Boot Header defines characteristics of the FSBL partition. The image ID and Header Checksum fields in the Boot Header allow the BootROM code to run integrity checks. The Encryption Status field specifies whether the FSBL is non-secure or secure, and if secure, whether the key source is eFUSE or BBRAM.


The Boot Header aka BootROM Header aka Boot Image Header



4. In this case, once the BootROM loads the FSBL into OCM from the QSPI it jumps to the FSBL running in OCM.


The FSBL:


I) Initializes the PS using the PS7 Init data that is generated by Vivado tools (MIO, DDR, etc.)

II) Programs the PL using a bitstream if a bitstream is included in the BOOT.bin built with bootgen.

III) Loads the bare-metal application code into DDR memory.

IV) Jumps to the bare-metal application


Reference


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