Flash Memory

System Flash

The Flash memory attached to the USB microcontroller stores device firmware and settings as well as user data that is accessible via the FrontPanel API.  The API includes three methods for accessing this memory: FlashEraseSectorFlashWrite, and FlashRead.  Please refer to the FrontPanel User’s Manual and the FrontPanel API Reference for information about applying these methods.

Layout

The system flash (Cypress S25FS128SAGBHI200 or similar) is a 16 MiB Flash memory arranged into 256 64-kiB sectors.  Each sector contains 256 256-byte pages.  Sectors 0…15 are reserved for device firmware and settings and are not accessible to user software.  The remaining 15 MiB may be erased, written, and read using the FrontPanel API at any time even without a valid FPGA configuration.  Full 64 kiB sectors must be erased at a time.  However, contents may be read or written on any page address boundary.

FPGA Flash

The SPI Flash attached to the FPGA is an ISSI IS25WP256D-JLLE or equivalent.  It provides non-volatile storage for use by the FPGA.

The Flash memory is connected to the FPGA through the configuration bank (Bank 0). The STARTUPE3 Xilinx primitive must be used to interface with the flash memory from a user design. See UG570 and the flashloader sample included with FrontPanel for more information.

The flash pins are connected to the configuration according to the table below:

FLASH PINCONFIGURATION PIN
SI/IO0D00_MOSI_0
SO/IO1D01_DIN_0
WPn/IO2D02_0
HOLDn/IO3D03_0
SCKFPGA_CCLK
CEnFPGA_RDWR_FCS_B

Loading a Power-On FPGA Configuration

The FPGA Flash may be used to store a Xilinx bitfile to configure the FPGA at power-on. The Flash can be written using FrontPanel or through Vivado with a Xilinx JTAG cable.

FrontPanel can be used to erase and program the power-on bitfile and the Flashloader sample is provided to perform these steps from a simple command-line utility.  Source code to the Flashloader sample is included with the FrontPanel SDK.

Using FrontPanel’s flash programming utility, apply the following settings:

  • Target: FPGA Flash
  • Data Type: Configuration
  • Start Sector: 0

Using the Flashloader sample, called with a single argument (the filename for a valid Xilinx bitfile), the Flashloader sample will erase the first sectors in the FPGA Flash, then write the bitfile.

An FPGA configuration loaded in the FPGA Flash will always load at power on until the flash memory containing the configuration is cleared.