The CC3235x device maintains a proprietary file system on the serial flash. The CC3235x file system stores the MCU binary, 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 at the beginning of the serial flash. The applications microcontroller must access the serial flash memory area allocated to the file system directly through the CC3235x file system. The applications microcontroller must not access the serial flash memory area directly.
The file system manages the allocation of serial flash 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 serial flash using human-readable filenames 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.
All file types can have a maximum of 100 supported files in the file system. All files are stored in 4-KB blocks and thus use a minimum of 4KB of flash space. Fail-safe files require 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 1MB.
Table 9-4 lists the minimum required memory consumption under the following assumptions:
|ITEM||CC3235S (KB)||CC3235SF (KB)|
|File system allocation table||20||20|
|System and configuration files(1)||256||256|
|Gang image size||256 + MCU||256 + MCU|
|Total||1308 + MCU||2844 + MCU|
|Minimal flash size(2)||16 MBit||32 MBit|
|Recommended flash size(2)||16 MBit||32 MBit|
The maximum supported serial flash size is 32MB (256Mb) (see Using Serial Flash on CC3135/CC3235 SimpleLink™ Wi-Fi® and Internet-of-Things Devices).