Open Source FAT File System, M3S-TFAT-Tiny (TFAT) is a FAT file system that only requires a small amount of memory. It is 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 the 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.


  • 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
Module Configuration


  • Compact design tailored for embedded systems
    Realizable using the internal memory of the microcontroller
    Approx. ROM 12.7KB Approx. RAM 4byte and the stack approx 200-byte
  • OS is unnecessary
  • The supplied sample programs include sample software for reading/writing files to MultiMediaCard on the CPU board which comes with the Renesas Starter Kit.
  • It also allows you to read/write files to an SD Memory Card and USB Flash drive.
  • Learn More

Release Information

Target Devices


Type Title Date
Application Note PDF 360 KB 日本語
Application Note PDF 294 KB 日本語
Application Note PDF 556 KB 日本語
Application Note PDF 850 KB 日本語
Tool News - Release PDF 266 KB 日本語
5 items

Design & Development

Sample Code

Additional Details


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 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 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 RL78 Family
IDE CS+ for CC V3.01.00
CS+ for CA,CX V3.01.00
IAR Embedded Workbench for RL78 Family provided by IAR Systems V.2.10.1
Applicable Compiler RL78 compiler CA78K0R V1.70 or later
RL78 compiler CC-RL V1.01 or later
IAR Embedded Workbench for Renesas RL78 V.2.10.1 or later
Occupied ROM Size Approx. 12.7KB
Occupied RAM Size Approx. 0.2KB *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