The CC3200 device maintains a proprietary file system on the SFLASH. The CC3200 file system stores the service pack file, system files, configuration files, certificate files, web page files, and user files. By using a format command through the API, users can provide the total size allocated for the file system. The starting address of the file system cannot be set and is always located at the beginning of the SFLASH. The applications microcontroller must access the SFLASH memory area allocated to the file system directly through the CC3200 file system. The applications microcontroller must not access the SFLASH memory area directly.

The file system manages the allocation of SFLASH blocks for stored files according to download order, which means that the location of a specific file is not fixed in all systems. Files are stored on SFLASH using human-readable file names rather than file IDs. The file system API works using plain text, and file encryption and decryption is invisible to the user. Encrypted files can be accessed only through the file system (see Figure 9-2).

All file types can have a maximum of 128 supported files in the file system. All files are stored in blocks of 4KB and thus use a minimum of 4KB of flash space. Encrypted files with fail-safe support and optional security are twice the original size and use a minimum of 8KB. Encrypted files are counted as fail safe in terms of space. The maximum file size is 16MB.

The CC3200 device supports JEDEC specification SFDP (serial flash device parameters). The following SFLASH devices are verified for functionality with the CC3200 device in addition to the ones in the reference design:

• Micron (N25Q128-A13BSE40): 128 Mb
• Spansion (S25FL208K): 8 Mb
• Winbond (W25Q16V): 16 Mb
• Adesto (AT25DF081A): 8 Mb
• Macronix (MX25L12835F-M2): 128 Mb

For compatibility with the CC3200 device, the SFLASH device must support the following commands:

• Command 0x9F (read the device ID [JEDEC]). Procedure: SEND 0x9F, READ 3 bytes.
• Command 0x05 (read the status of the SFLASH). Procedure: SEND 0x05, READ 1 byte. Assume bit 0 is busy and bit 1 is write enable.
• Command 0x06 (set write enable). Procedure: SEND 0x06, read status until write-enable bit is set.
• Command 0xC7 (chip erase). Procedure: SEND 0xC7, read status until busy bit is cleared.
• Command 0x03 (read data). Procedure: SEND 0x03, SEND 24-bit address, read n bytes.
• Command 0x02 (write page). Procedure: SEND 0x02, SEND 24-bit address, write n bytes (0 < n < 256).
• Command 0x20 (sector erase). Procedure: SEND 0x20, SEND 24-bit address, read status until busy bit is cleared. Sector size is always assumed to be 4K.