Open Source FAT File System

M3S-TFAT-Tiny (TFAT) is a FAT file system that only requires a small amount of memory. This is based on open source FatFs . In addition, this is also Firmware Integration Technology (FIT) and can be combined with other FIT modules.

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.


TFAT for RX family V.4.01 (FatFs R0.13c) supports new memory storages, eMMC and Serial Flash memory. You can also use format feature for eMMC and Serial Flash memory with TFAT (excluded SD memory card and USB memory).

Learn More (Application Note) >>

Release Information

Target Device Software Name Version/Release Date Status
RX Family M3S-TFAT-Tiny for the RX Family Latest Version: V.4.01
Released: Jul. 27, 2020

Upgrade Details

Operating Environment

Related Application Notes


  • 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)
  • Supported CC-RX, IAR and GCC compilers
  • Supported both of none RTOS and RTOS (FreeRTOS and RI600V4)


  • File system software
  • Sample program that supports Renesas integrated development environment.
  • API 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 read/write 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_rename Renames or moves a file or a directory
f_tell Get current read/write pointer
f_eof Test for end-of-file
f_size Get file size
f_error Test for an error
f_mkfs Format a volume as FAT file system
disk_initialize Initializes a drive Note
disk_read Reads from a drive Note
disk_write Writes to a drive Note
disk_ioctl Controls drive I/O Note
disk_status Gets drive status Note
get_fattime Gets date and time Note


The TFAT module is not designed for use with a specific piece of hardware and therefore does not include these functions (drivers). In fact, the M3S-TFAT-Tiny memory driver interface module Firmware Integration Technology (TFAT driver FIT) includes these functions.

Operating Environment

Target Device RX Family
Applicable Compiler
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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