This 16-bit DOS program was developed during the years 1994 to 1999.

ADF v1.50 serial port FOSSIL driver


28888 bytes
Jan 19, 2000
Click on file name to download (or use Save Link As...).

ADF is a serial port FOSSIL driver for high speed modem users. Supports FIFO UARTs 16550, 16650 and 16750, 115200 bps, any port, any IRQ, any FIFO trigger level, FOSSIL rev level 5 and multitasking environments (such as Windows 3, Windows 95 and OS/2).

Original source code


46514 bytes
Jun 9, 2021
Click on file name to download (or use Save Link As...).

The assembly language source code has been made available to the public by the author.

What is a FOSSIL?

A FOSSIL is a kind of serial port device driver used by other programs to access the serial port. It is mainly used by BBS programs, and is very common in FidoNet programs.


ADF is a FOSSIL revision level 5 driver, including the additional functions defined by Raymond L. Gwinn in X00 v1.50.

ADF is specially designed for users of high speed modems with or without the 16550, 16650 or the 16750 UART, using DOS or a multitasking environment.

ADF was initially written some years ago because other FOSSIL drivers did not always work properly in protected mode multitasking environments, where the UART is emulated.

ADF is designed to work well with both emulated UARTs and real UARTs, without any drawbacks.

Features of ADF

  • Always a locked baud-rate.
  • Locked baud-rate of any speed (2 bps - 115200 bps).
  • Defaults to 8 databits, no parity, and 1 stop bit (8N1).
  • Always CTS/RTS handshake. Never DSR/DTR or XON/XOFF handshake.
  • One port per ADF (load ADF in different tasks for many ports).
  • COM-port address configurable (0H-FFFFH).
  • COM-port IRQ configurable (0-15).
  • Full support of the 16550, 16650 and 16750 UARTs.
  • Fills transmit 16550-FIFO buffer with all 16 bytes.
  • Fills transmit 16650-FIFO buffer with all 32 bytes.
  • Fills transmit 16750-FIFO buffer with all 64 bytes.
  • Receiver 16550-FIFO configurable (1, 4, 8 or 14 bytes).
  • Receiver and transmitter 16650-FIFO configurable.
  • Receiver 16750-FIFO configurable.
  • Only 8088/8086 compatible code used.

v1.50 January 19, 2000

  • Changed from shareware to freeware. No registration needed anymore.

v1.46 July 13, 1999

  • Some more functions in ADFTerm added for terminating program with FOSSIL kept opened.
  • The manual updated.
  • REGISTER.EXE v1.40 needed to register.

v1.45 January 1, 1999

  • ADF uses 16 bytes transmit FIFO for 16750, and not 64 bytes as before. The TL16C750 data sheet from December 1997, says that only 16 bytes may be written into the transmit FIFO at one time.

v1.44 January 12, 1998

  • The FidoNet address 2:203/620 is no longer valid, and has been removed from the programs and documentation.
  • REGISTER.EXE v1.30 needed to register.

v1.43 March 9, 1997

  • has replaced as the registration e-mail address.

v1.42 November 3, 1996

  • Support of 16750 UART with 64 bytes FIFO.
  • The FOSSIL is now always kept alive, it is never actually closed, until ADF is unloaded. Applications, including the DOS devices COM1: and COM2:, that uses the BIOS serial communication functions, will because of this now use the FOSSIL functions when ADF is loaded.
  • AnDan Software is now on the WWW at
  • The chapter about benchmarks has been removed, because some users misunderstand its purpose.
  • Does not touch 16650/16750 register if not 16650/16750 has been set on command line, else Windows may crash.
  • The internal size of receive and transmit buffers adjusted so the reported sizes will be equal to the sizes on the command line.
  • Due to behavior in Windows 95 when ADF is loaded in AUTOEXEC.BAT (not recommended), the Priority Interrupt Controller enable bits are toggled on initialization calls to the FOSSIL.
Copyright © 1996-2024 Scandinavian Digital Systems AB
Developed by Anders Danielsson