Open Source FAT File System

M3S-TFAT-Tiny (TFAT) is a FAT file system that only requires a small amount of memory.

Renesas has various MCUs, including the RX Family, that are suitable for use in applications such as single-function home appliances and compact industrial equipment, where the incorporation of more sophisticated functionality or the newest technology, with a negligible increase in cost, is desired. To support such development activities, Renesas offers software libraries with only the essential features for application, at low cost.

Use TFAT in any device incorporating a target microcontroller for functions such as accumulating measured or archived data, or rewriting a stored program via memory card. Although TFAT is a FAT file system, and PC data exchange capability enable analysis and management of data by a PC application.

TFAT supports various types of memory devices. The supplied sample programs include sample software for reading/writing files to SD Memory card and USB Flash drive on the CPU board which comes with the Renesas Starter Kit.


M3S-TFAT-Tiny V.3.04 released. Supported download and import sample projects of FIT modules with the Smart Configurator.

Release Information

Target Device Software Name Version/Release Date Status
RX Family M3S-TFAT-Tiny for the RX Family Latest Version: V.3.04 Release 00
Released: January 21, 2019

Upgrade Details

Operating Environment

Related Application Notes

*The Application Notes and Sample Code of TFAT for the MCUs are available. Please download from the Sample Code tab for this page.


  • Compact design tailored for embedded systems
    Realizable using the internal memory of the microcontroller
    Approx. 8.9KB ROM and approx. 900B RAM (for the RX Family)
  • OS is unnecessary


  • File system software (binary format library)
  • Sample program that supports Renesas integrated development environment.
  • Library function user's manual and other documents in a complete set

Modular Composition

Modular Composition


Function Name Description
f_mount Mounts a volume
f_open Opens a file
f_close Closes a file
f_read Reads from a file
f_write Writes to a file
f_lseek Moves the file pointer
f_truncate Truncates a file
f_sync Flushes the cache
f_opendir Opens a directory
f_readdir Reads a directory
f_getfree Gets free area
f_stat Gets file status
f_mkdir Makes a directory
f_unlink Deletes a file or a directory
f_chmod Changes properties of a file or a directory
f_utime Changes time property of a file or a directory
f_rename Renames or moves a file or a directory
disk_initialize Initializes a drive (Note1)
disk_read Reads from a drive (Note1)
disk_write Writes to a drive (Note1)
disk_ioctl Controls drive I/O (Note1)
disk_status Gets drive status (Note1)
get_fattime Gets date and time


The functions need to be created on the customer side as suitable for the hardware used. The TFAT library is not designed for use with a specific piece of hardware and therefore does not include these functions (drivers).

Operating Environment

Target Device RX Family
Applicable Compiler C/C++ Compiler Package for RX Family V.1.02 Release 01 or later
Occupied ROM Size Approx. 8.9KB
Occupied RAM Size Approx. 0.9KB *including the stack


Examples of application field:

  • Data preservation and data logging in various types of equipment
    • Preservation of number of revolutions, temperature and other data in industrial equipment
    • Preservation of a history of operations and settings alteration for remote equipment failure diagnostic
  • Preservation of personal information in health equipment and similar other equipment used individually
    • Preservation of heart rate and blood pressure data in health equipment
    • Preservation of physical exercise data in training equipment
  • Updating of programs and data in various types of equipment
    • Flash memory rewriting with programs or data stored in a memory card in places where equipment is installed

Development Tools Support

Title Description
My Renesas Create a My Renesas account to use our tool download services, receive e-newsletter/update notifications and take advantage of our other services.
e-learning Information for studying and learning about microcontrollers and microprocessors.
FAQ Frequently asked questions and useful hints for development.
Forum A forum and community site to share technical information, questions and opinions with others who use Renesas MCUs.
Tool News Tool release information and other important information.
Operating Environment Information on system requirements and operating environment for the latest version of the tools.
Information on Discontinued Products A list of Renesas software and tools that have been discontinued and are no longer being offered for new projects.

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