             Functions Reference Manual for the ONEFOSsil Developer
            (C) Copyright 1995-96 by Carl Morris and Morris Softronics
         ONEFOSsil, A low level serial communications driver for MS-DOS
                     based FOSSIL 5 compliant applications.

                                  Introduction

    This document is for developers wanting to use ONEFOSsil specific
    features and for developers just learning about the FOSSIL
    specification.  ONEFOSsil supports most FOSSIL 5 and X00 extended
    functions, and this document will help describe any differences.
    Portions of this document are copyright by VEP Software, Rick Moore, and
    Raymond Gwinn.  The rest of this document is copyright by Morris
    Softronics and Carl Morris.

    This documentation is distributed as is and is provided with no
    guarantees.  You use the information contained within at your own risk.

                     What is ONEFOSsil and a FOSSIL driver?

    ONEFOSsil is a simplified serial communications driver for 8250 series
    UART's and MS-DOS based machines running applications requiring a simple
    FOSSIL 5 communications driver.  ONEFOSsil only provides FOSSIL based
    services.

    FOSSIL is an acronym derived from Fido Opus Seadog Standard Interface
    Layer.  The FOSSIL specification was intended to permit machine
    independent software (Fido, Opus, and Seadog at the time) to be created
    and ran on any MS-DOS based 8086 based computer that had a FOSSIL
    compatible driver.  Those days are much over, and FOSSIL compatible
    drivers are only used as a low level communications interface for
    application software.  A better specification is needed to keep up with
    today's quickly changing world, though.

    ONEFOSsil does not maintain total compatibility with the FOSSIL 5
    specification.  These differences will be noted in this document, but
    will seldom cause problems with most modern software.

                                   Interface

    ONEFOSsil's Application Program Interface is partly based on the PC BIOS
    communications interface.  As such, the driver will be entered with an
    8086 instruction INT 14h.  A function number is passed in 8086 register
    AH and other registers are used as needed.  Return codes from functions
    will very from function to function, and is one of the most confusing
    aspect of FOSSIL programming; they're not logical!

    Registers are not modified by ONEFOSsil unless otherwise specified.
    Note that this is not true about all FOSSIL drivers.  While this
    document covers basic FOSSIL functions, some differences will be
    encountered from FOSSIL to FOSSIL.

    In most cases, functions will require a port number to operate.  In all
    cases, port numbers are passed in register DX.  Most FOSSIL's only
    support ports 0 - 7.  FOSSIL to DigiBoard converters usually only
    support 0 - 15.  ONEFOSsil supports ports 0 - 63.  Notice that in most
    cases, the port number is one less than the COM port number; but, in
    most FOSSIL's, the port can be specified on any address/irq combination,
    or may not even map to a COM port at all.

    As a note to developers, FOSSIL functions should not be called in a way
    that could cause active code to be reentered.  ONEFOSsil and many other
    FOSSIL's are re-entrant, but not to that great of a degree.

                                   Detection
    Detecting FOSSIL drivers vary.  The FOSSIL specification states that to
    detect a FOSSIL, one should look at the 6th byte (3rd word) after the
    start of the INT 14h service routine for the word 1954h, followed by a
    byte, the maximum function supported by the FOSSIL driver.  However,
    this is unreliable if other utilities and/or drivers have hooked the INT
    14h interrupt vector since the FOSSIL was loaded.  It is not suggested
    to use this method.  Instead, it is better to just make the call to the
    "Activate" function 04h for the port you want to open and check its
    return codes.  Almost all current applications detect the FOSSIL in this
    way.  Another method, which only works for a few drivers, is to call the
    "Information" function, and check its return codes.  X00 only works
    correctly if the FOSSIL port called is active.  ONEFOSsil and BNU work
    all the time.  Refer to function 1Bh for more information on the
    "Information" function; however, this method is not suggested either.

                                   Functions

    The following functions are supported by most FOSSIL drivers.

    Function 00h - Set communications baud, parity, etc.

         Input:
              AH = 00h
              AL = Communications parameters:
                  010----- = 300 baud
                  011----- = 600 baud
                  100----- = 1200 baud
                  101----- = 2400 baud
                  110----- = 4800 baud
                  111----- = 9600 baud
                  000----- = 19200 baud (replaces IBM 110 baud setting)
                  001----- = 38400 baud (replaces IBM 150 baud setting)
                  ----0--- = No parity
                  ---01--- = Odd parity
                  ---11--- = Even parity
                  -----0-- = 1 stop bit;
                  -----1-- = 1 bits for 5-bit byte length, 2 for all
                             others
                  ------00 = 5 bits
                  ------01 = 6 bits
                  ------10 = 7 bits
                  ------11 = 8 bits
              DX = Port number
              BX = 0 (incase BNU tries to extend this function)

         Output:
              AH = Line status (see function 03h)
              AL = Modem status (see function 03h)

         This function is identical to the IBM PC INT 14h BIOS call except
         that 110 baud and 150 baud have been replaced by 19200 baud and
         38400 baud respectively.  See function 1Eh for an enhanced version
         of this function.  In addition, once function 1Eh has been used,
         this function will not change the baud rate until function 04h is
         used to reactivate the FOSSIL driver.

         Note that BNU contains an extension to this function, and that if
         that extension is not desired you should make sure that BX and CX
         are not equal, or that one of them are zero.  If you would like
         information on this extension please write the author of this
         document or David Nugent, author of BNU.

    Function 01h - Transmit character with wait.         Input:

              AH = 01h
              AL = Output character
              DX = Port number

         Output:
              AH = Line status (see function 03h)
                  1------- = Time-out occurred, all other bits void
                  0------- = Character buffered, all bits valid
              AL = Modem status (see function 03h, void if time-out
              occurred)

         If there is no room in the transmit buffer, this function will wait
         until there is room in the buffer or until a time-out occurs.

         Notes:

           X00 executes functions with the interrupt mask set as it was
           when entered.  That is, if X00 is called with interrupts masked,
           interrupts will remain masked during the processing of the
           function.  If this function is called with interrupts masked, it
           may never return.
           ONEFOSsil always enables interrupts upon the beginning of every
           FOSSIL call, so unless there are severe hardware problems,
           ONEFOSsil should always return.
           It is suggested that applications use function 0Bh instead of
           this function in all cases.  This function is slow, and X00 and
           BNU are prone to lock-ups.  Even if the THRE bit is set in a
           status return, there is a chance that the buffer could be filled
           by another application between calls, and as such the correct
           application would get a long, unnecessary delay before control
           is returned.
           Many applications do not check the returned status for a time-
           out condition, and as such drop characters when time-outs occur.

    Function 02h - Get received character with wait.

         Input:
              AH = 02h
              DX = Port number

         Output:
              AH = Line status (see function 03h)
                  1------- = Time-out occurred, all other bits void
                  0------- = Character returned, all bits valid
              AL = Input character (if no time-out occurred)

         If no character is available from the receive buffer, this function
         will wait until a character is received or until a time-out occurs.

         Notes:

           X00 executes functions with the interrupt mask set as it was
           when entered.  That is, if X00 is called with interrupts masked,
           interrupts will remain masked during the processing of the
           function.  If this function is called with interrupts masked, it
           may never return.
           ONEFOSsil always enables interrupts upon the beginning of every
           FOSSIL call, so unless there are severe hardware problems,
           ONEFOSsil should always return.
           It is suggested that applications do not use this function.  It
           is slow, and X00 and BNU are prone to lock-ups.  Even if the RDA
           bit is set in a status return, it is possible that another
           application could steal the character, leaving the correct
           application to wait for the next character or a time-out.  It is
           suggested that function 18h be used instead.  Function 18h
           always returns immediately.  Sample code for calling this block
           function in a single character mode can be found in the
           applications notes.  Also, X00 and ONEFOSsil support a "get
           character with no wait" at function 20h, but is not supported by
           the FOSSIL 5 specification or most other FOSSIL's.

    Function 03h - Return serial port status.

         Input:
              AH = 03h
              DX = Port number

         Output:
              AH = Line Status (resembles the 8250 Line Status Register)
                  1------- = time-out, all other bits in AH and AL void*
                  -1------ = TSRE, output buffer is empty*
                  --1----- = THRE, room is available in output buffer*
                  ---1---- = BRK, break detected (since last return)
                  ----1--- = FE, framing error detected (since last return)
                  -----1-- = PE, parity error detected (since last return)
                  ------1- = OE, the input buffer has overrun (since last
                             return)*
                  -------1 = RDA, received data is available in buffer*
              AL = Modem Status (resembles the 8250 Modem Status Register)
                  1------- = Data carrier detect (DCD)*
                  -1------ = Ring indicator (RI)
                  --1----- = Data set ready (DSR)
                  ---1---- = Clear to send (CTS)
                  ----1--- = Always set to 1 upon return (dummy DCD)*
                  ----1--- = Delta data carrier detect (since last return)
                  -----1-- = Trailing edge ring indicator (since last
                             return)
                  ------1- = Delta data set ready (since last return)
                  -------1 = Delta clear to send (since last return)

         * Denotes formal FOSSIL 5 specified bits.

         The FOSSIL specification calls for the delta data carrier detect
         bit to always be set to act as a dummy DCD.  If an application
         needs a dummy DCD, it should implement it internally as described
         in the notes below.  As such ONEFOSsil does not support it and
         instead uses the bit as a Delta Data Carrier Detect.  ONEFOSsil
         instead includes a command line option to fake Data Carrier Detect.

         Notes:

           All bits without asterisks (*) will vary in meaning from FOSSIL
           to FOSSIL driver.
           X00 does not attempt to accurately return the Delta bits.
           ONEFOSsil should correctly return the status of the Delta bits.
           One way to implement a dummy DCD is to check the DCD at the
           start of the connection.  If DCD is active, the real DCD should
           be watched.  If DCD is inactive, it should be assumed that there
           might never be a DCD, and assume an internal dummy DCD.  If DCD
           was to go active at some later time, real DCD watching should be
           re-enabled and used from there out.  However, with ONEFOSsil
           supporting command line options for faking DCD, it is not
           suggested to follow the above practice.

    Function 04h - Activate Port.

         Input:
              AH = 04h
              BX = 0h (in case the FOSSIL supports Control-C flagging)
              DX = Port number

         Output:
              AX = 1954h if successful
              BL = Maximum function number supported
              BH = Revision of FOSSIL specification supported

         This function instructs the FOSSIL driver to initialize itself for
         communications on the specified port.  Buffers will be cleared,
         interrupts activated, and DTR raised.  If the port can not be
         supported, the call goes to the next driver or to the system BIOS.

         The FOSSIL specification states that the port parameters are not to
         be initialized at this time.  However, with ONEFOSsil, if port
         parameters have been locked on the command line, they will be
         loaded during this time.

         The FOSSIL specification calls for an optional Control-C flag, and
         is not supported by X00 or ONEFOSsil.  As such, BX should be
         cleared to prevent any possibility of this occurring.

         X00 incorrectly returns the maximum function number (or it isn't
         documented.)  BNU and ONEFOSsil will only return the maximum
         function (currently 20h in ONEFOSsil.)  BNU has an option to be
         compatible with the bug X00 has also.

         Multiple calls to this function will repeat the above process as
         if the port had not been open.  If you want to insure the port is
         closed before opening, call function 05h first (many BBS's and
         doors do this.)

         Notes:

           At some future date, Ray Gwinn intends to make this function
           identical to the PS/2's function 04h.  Function 1Ch is a
           duplicate of this function.  It is my intention to create a new
           standard that will support this, and permit much better
           communications over all devices available.  I do not; however,
           have any opinion on which call should be made.  The latest X00
           and VX00 still support both functions.
           Calling this function with an invalid port number will not
           return a valid reponse.  Any application which calls this
           function with port number 255 is in error!

    Function 05h - Deactivate Port.

         Input: AH = 05h
                DX = Port number

         Output:   Nothing

         This function instructs the FOSSIL that it should no longer process
         calls for specified port using the FOSSIL specification.  This
         function is passed on to the next driver if the port is not active.
         Any additional calls to this driver with the specified port will
         also be sent on the next driver or the PC BIOS.  Any function not
         needing a port number, or an active port, will be processed by most
         FOSSIL drivers.  X00 will not process "Information" requests if the
         port requested is not
         active.

         ONEFOSsil will attempt to flush the buffers before this function
         will return.  ONEFOSsil will return if a time-out occurs, after
         deactivating the port.  This is to help buggy software that
         deactivate the port before all of their "closing" screen has been
         sent.  It should be assumed however that what is in the transmit
         buffer will be lost when this function is called.

         NOTICE:  With Revision 9, ONEFOSsil will nolonger flush the port.
         This created an extra long delay under some circuimstances, and if
         application authors can't get it right on their own, ONEFOSsil
         isn't going to cover up for them.

         NOTICE: At some future date, Ray Gwinn intends to make this
         function identical to the PS/2's function 05h.  Function 1Dh is a
         duplicate of this function.  It is my intention to create a new
         standard that will support this, and permit much better
         communications over all devices available.  I do not; however, have
         any opinion on which call should be made.  The latest X00 and VX00
         still support both functions.

    Function 06h - Raise/lower DTR.

         Input: AH = 06h
                AL = DTR state to set
                DX = Port number

         Output:   Nothing

         This function is used to control the DTR signal.  AL is defined as
         follows:

                00h = lower DTR
                01h = raise DTR

         With ONEFOSsil and most other FOSSILs, any even value will lower
         the DTR, any odd value will raise the DTR.

         No other function (except functions 04h, 1Ch, and 1Fh) will alter
         DTR.

    Function 07h - Return timer tick information.

         Input: AH = 07h

         Output:   AL = Timer tick interrupt number (1Ch or 08h)
                AH = Approximate interrupts per second (18 on IBM)
                DX = Approximate number of milliseconds per tick (55)

         This function is used to determine the characteristic of the timer
         tick for the computer.

         The FOSSIL specification says this function is to return the
         interrupt number, not the vector.  However, most FOSSIL's seem to
         return the vector.  ONEFOSsil also returns the vector, 1Ch.

         This function useless today.  I would instead like to see some
         functions that do the timing internally, including calculating the
         time in seconds for the application.  There would need to be 5 or 6
         timers in each port, to allow both BBS's and DOOR software to do
         separate timing.  BBS and DOOR software could use a single downward
         counter/timer for time left on-line, but to actually see software
         implement this would be a miracle.

    Function 08h - Flush output buffer.

         Input: AH = 08h
                DX = Port number

         Output:   Nothing

         This function is used to wait until all pending output has been
         transmitted.  It does not return until all buffered output has been
         sent.

         This function should be used with care.  Flow control can cause the
         system to hang in a tight un-interruptible loop given the right
         circumstances.

         Note:  X00 executes functions with the interrupt mask set as it was
         when entered.  That is, if X00 is called with interrupts masked,
         interrupts will remain masked during the processing of the
         function.  If this function is called with interrupts masked, it
         may never return.

         ONEFOSsil will not wait indefinitely and always enables interrupts.
         ONEFOSsil will return if no output has been transmitted in the
         time-out period.  There is no status returned to notify the
         application of this condition.

         ONEFOSsil's deactivate function literally calls this function to
         flush the output buffer.

         It is advised that this function NOT be used due to the problems
         that could arise.  Instead developers are asked to use function 03h
         and wait in their own loop while the TSRE bit is clear.  This would
         permit the application to keep an eye on local keyboard activity
         among other things.

    Function 09h - Purge output buffer.

         Input: AH = 09h
                DX = Port number

         Output:   Nothing

         This function is used to remove any buffered output (transmit)
         data.  Any output data remaining in the output buffer (not
         transmitted yet) is discarded.

    Function 0Ah - Purge input buffer.

         Input: AH = 0Ah
                DX = Port number

         Output:   Nothing

         This function is used to remove any buffered input (received) data.
         Any input data which is in the receive buffer is discarded.

    Function 0Bh - Transmit no wait.

         Input: AH = 0Bh
                AL = Character
                DX = Port number

         Output:   AX > 0000h - Character was buffered for transmission
                   = 0000h - Character was not buffered

         This function performs the same operation as function 01h except
         control is returned even if there is no room in the buffer.

         It is requested that developers use this function for single
         character transmissions.  It is asked that you also look into using
         function 19h which can transmit more than one character at a time.
    Function 0Ch - Non-destructive read-ahead (Peek).

         Input: AH = 0Ch
                DX = Port number

         Output:   AH = 00h if a character is available
                   > 00h if no character is available
                AL = Next character if available

         This function returns the next character from the receive buffer.
         The character returned remains in the receive buffer.  Some
         programmers call this function "peek".

         The extended function 20h is a destructive read without wait.

    Function 0Dh - Keyboard peek without wait.

         Input: AH = 0Dh

         Output:   AX = IBM-style scan code if available
                   = 0FFFFh if no character is available

         This function returns the keyboard scan code of the next character
         from the keyboard.  This is a non-destructive (peek) read of the
         keyboard.

         This function should not be used by IBM PC software.

    Function 0Eh - Keyboard read with wait.

         Input: AH = 0Eh

         Output:   AX = Keyboard scan code

         This function returns the next character available from the
         keyboard.  If no keyboard input is available, this function waits
         until a keyboard character is available.  Returned character codes
         are the same as function 0Dh (IBM style scan codes).

         This function should not be used by IBM PC software.

    Function 0Fh - Flow Control for serial I/O.

         Input: AH = 0Fh
                AL = Bit defining the flow control to use
                DX = Port number

         Output:   Nothing

         Two kinds of basic flow control are supported.  One is software,
         called Xon/Xoff flow control.  The other is hardware, called
         RTS/CTS flow control.  Both software and hardware flow control may
         be enabled and used at the same time.

         The bits passed in AL are defined as follows:

                Bit 0 = 1    Enable receiving of Xon/Xoff
                Bit 1 = 1    Enable RTS/CTS flow control
                Bit 2        Reserved (should be zero)
                Bit 3 = 1    Enable transmitting of Xon/Xoff

         The FOSSIL specification states that all other bits should be set
         to 1 for future expansion.  This is insane, as it might enable
         options the application doesn't want.  It is simpler to assume that
         if the bit is not used now, you wont need to use it later and leave
         it cleared.

         ONEFOSsil permits controlling and locking these options on the
         command line.  As such, a request to enable or disable a flow
         control may not be honored.

         Some other FOSSIL drivers automatically lock RTS/CTS if the baud
         rate or data parameters are locked on the command line.

    Function 10h - Control-C/K checking and transmitter control.

         Input: AH = 10h
                AL = Control bits (defined below)
                DX = Port number

         Output:   AX = 0001h - A Control-C/K has been received
                   = 0000h - A Control-C/K has not been received

         This is primarily used for BBS operation.  A bit mask is passed in
         AL with the following flags:

                Bit 0 = 1    Enable Control-C/K checking
                Bit 1 = 1    Disable the transmitter

         The Control-C/K status is only returned as long as Control-C/K
         checking is enabled.  The status is cleared after each call.

         The transmitter disable bit lets the application program inhibit
         the transmitter.  FIFO's of 16550's can not be stopped, and will
         continue to transmit until empty.

         The disable of the transmitter is not absolute.  Several internal
         functions can cause the transmitter to be re-enabled, such as
         attempting to store another character in the buffer.  Some FOSSIL's
         will also re-enable the transmitter when they receive an Xon, but
         ONEFOSsil does not.

    Function 11h - Set current cursor location.

         Input: AH = 11h
                DH = Row (line)
                DL = Column

         Output:   Nothing

         This function is exactly like INT 10h, sub-function 2, on the IBM
         PC.  The row and column are relative to zero.  That is, the home
         position on the screen is row 0, column 0.

         This function should not be used by IBM PC software.

    Function 12h - Read current cursor location.

         Input: AH = 12h

         Output:   DH = Row (line)
                DL = Column

         This function is exactly like INT 10h, sub-function 3, on the IBM
         PC.  The current cursor location (using the same coordinate system
         as function 16h) is returned in DX.

         This function should not be used by IBM PC software.

    Function 13h - Single character ANSI write to screen.

         Input: AH = 13h
                AL = Character to display

         Output:   Nothing

         The character passed in AL is sent displayed on the screen at the
         current cursor location.   ANSI.SYS type processing is performed.
         This routine should not be used in such a way that DOS output
         (which is not re-entrant) can not be employed by the FOSSIL to
         execute the function.

         ANSI.SYS is used by most FOSSIL drivers on the IBM PC.

         This function should not be used on IBM PC software.

    Function 14h - Enable or disable the DCD watchdog.

         Input: AH = 14h
                AL = 01h - Enable watchdog
                   = 00h - Disable watchdog
                DX = Port number

         Output:   Nothing

         This function enables and disables the monitoring of carrier
         detect.  When enabled, the state of the carrier detect (DCD) is
         constantly monitored during timer tick processing.  Should carrier
         detect be lost (turned off), the system will be re-booted.
         Activate/deactivate have no effect on the state of the DCD
         watchdog.

         This function is not supported by ONEFOSsil, and is dangerous in
         many multitasking environments.

    Function 15h - Write character to screen using BIOS.

         Input: AH = 15h
                AL = Character to display

         Output:   Nothing

         The specified character is sent to the screen using BIOS-level
         input/output routines.  This differs from function 13h in that DOS
         I/O will not be used.

         This function should not be used by IBM PC software.

    Function 16h - Add or delete a routine from the timer tick chain.

         Input: AH = 16h
                AL = 01h - Add a function
                   = 00h - Delete a function
                ES = Segment of function
                DX = Offset of function

         Output:   AX < 0FFFFh if operation is successful
                   = 0FFFFh if operation unsuccessful

         This function is used to allow a central authority to manage the
         timer interrupts, so that the integrity of the "timer tick chain"
         is not compromised.  Rather than using the traditional method of
         saving the old contents of the timer vector, storing the address of
         your routine there, and calling the "old" routine, instead you call
         this function.  The FOSSIL manages a list of such entry points and
         calls them on a timer tick (interrupt) using a FAR call.

         X00 will allow up to 4 programs to hook into the timer tick.
         Interrupts are enabled when the hooked routines are called.

         CAUTION:  When this FOSSIL function was implemented, it provided
         the best means to hook into the timer tick on multitasking systems
         at that time.  However, with the 80386 and virtual 8086 mode of
         operation used by DESQview, Windows V3.0+ etc., this function can
         crash the system.  The reason is the virtual 8086 application
         (task/window) that hooked in, may not be the active virtual 8086
         (task/window) when the timer tick interrupt occurs.

         Due to popularity of the virtual 8086 type multi-tasking systems,
         Ray Gwinn (who originally insisted that this function be created)
         RECOMMENDS THAT THIS FUNCTION NOT BE USED.

         ONEFOSsil returns 0FFFFh in AX at all times.  Happy Ray?

    Function 17h - Reboot system.

         Input: AH = 17h
                AL = 00h - "Cold boot"
                   = 01h - "Warm boot"

         Output:   Nothing

         This function is intended primarily as a security feature.  It
         provides the application with a last resort escape from a situation
         that could allow a security breach.

         ONEFOSsil attempts to close the task that made the call, rather
         than rebooting what could be a multi-user system.

         This function should not be called by ANY software.

    Function 18h - Block Read.

         Input: AH = 18h
                CX = Requested number of characters to transfer
                DX = Port number
                ES = Segment of the caller's buffer
                DI = Offset of the caller's buffer

         Output:   AX = Number of characters actually transferred

         This function will transfer from 0 to 65535 characters from the
         inbound circular buffer to the caller's buffer.  ES and DI are not
         modified by this function.  The number returned in AX will be the
         lesser of the caller's requested amount or the entire contents (if
         any) of the receive buffer.

         I request that this function be used even for reading a single
         character at a time.  The following examples to help:

         In ASM

              push bp        ;save frame pointer
              mov  bp,sp          ;set it
              xor  ax,ax          ;clear temp. value
              push ax        ;temporary storage
              mov  ah,18h    ;function call 18h
              mov  cx,1      ;get 1 byte
              mov  dx,port   ;port number
              lea  di,[bp-2] ;address of temp. storage
              push ss
              pop  es        ;move registers (size conscious)
              int  14h       ;make call
              or   ax,ax          ;any data moved?
              jnz  @F        ;data was moved
              mov  [bp-1],0FFh    ;write AH to 0xFF
         @@:  pop  ax        ;if AH = 0, AL = character
              pop  bp

         In C/C++

              No real example available as I would use in-line ASM to
              accomplish the function very similar to the above code.  Other
              people would use "regs" and "int86" calls.

         Notice that you could detect if function 20h is available, and use
         it when possible.  FOSSILC, my C/C++ FOSSIL routines (freeware) do
         exactly that.

         This function should especially be used by file transfer protocol
         software.

    Function 19h - Block Write.

         Input: AH = 19h
                CX = Requested number of characters to transfer
                DX = Port number
                ES = Segment of the caller's buffer
                DI = Offset of the caller's buffer

         Output:   AX = Number of characters actually transferred

         This function will transfer from 0 to 65535 characters to the
         outbound circular buffer.  ES and DI are not modified by this
         function.  The number returned in AX will be the lesser of the
         caller's requested amount or the amount (if any) required to fill
         the transmit buffer.

         This function should be used whenever possible!

    Function 1Ah - Break begin or end.

         Input: AH = 1Ah
                AL = 01h - Start sending 'break'
                   = 00h - Stop sending 'break'
                DX = port number

         Output:   Nothing

         This function will start or terminate a break signal.  This
         function is useful for activating command mode on some modems.  The
         application program is responsible for the timing of the BREAK.  If
         ONEFOSsil has been restrained by an Xoff received from the modem,
         the flag will be cleared.  Any port setting functions (including
         04h and 1Ch) will stop an in progress break.

         A break must be maintained long enough for the UART to have sent a
         full data byte at the current settings.  A break is a condition
         where the serial line maintains the state of a start bit for a full
         byte length.

    Function 1Bh - Return information about FOSSIL.

         Input: AH = 1Bh
                CX = Size of caller's info buffer in bytes
                DX = Port number
                ES = Segment of caller's info buffer
                DI = Offset of caller's info buffer

         Output:   AX = Number of bytes actually transferred

         X00 returns the following:

                CX = '0X'    First 2 bytes of 'X00 ' string
                DX = ' 0'    Second 2 bytes of 'X00 ' string

         ONEFOSsil returns the following:

                BX = 'ON'    No specific byte ordering, just the word
                CX = 'E '    "ONE " if you were to look at it in a register
                             dump.

         This function will transfer information about the selected port and
         its status to the caller.  This function is intended to assist
         "generic" applications to adjust to the current environment.

         Very little information should be used from the returned
         information.  An application should NOT use the buffer size or
         buffer free information for anything.  Use function 03h for
         information about the buffers.

         X00 returns the port status (function 03h) if this function is
         called for an inactive port.  BNU and ONEFOSsil return useful
         information if they support the port.

         X00 does not always return the following BAUD byte correctly.
         ONEFOSsil contains extra fields in the following structure.

         The data structure (assembly language style) currently returned by
         ONEFOSsil is as follows:

              INFO   EQU  $            ;DEFINE BEGIN OF STRUCTURE
              STRSIZ DW   INFO_SIZE    ;SIZE OF THIS STRUC IN BYTES
              MAJVER DB   CURR_FOSSIL  ;FOSSIL SPECIFICATION REV
              MINVER DB   CURR_REV     ;REVISION OF THIS DRIVER.
              IDENT  DD   ID_STRING    ;"FAR" POINTER TO ASCIIZ
                                       ; DRIVER DESCRIPTION STRING.
              IBUFR  DW   IBSIZE       ;BYTE SIZE OF THE INPUT BUFFER
              IFREE  DW   ?            ;BYTES OF RECV BUFFER FREE
              OBUFR  DW   OBSIZE       ;BYTE SIZE OF THE XMIT BUFFER
              OFREE  DW   ?            ;BYTES OF XMIT BUFFER FREE
              SWIDTH DB   SCREEN_WIDTH ;WIDTH OF DISPLAY SCREEN
              SHEIGHT DB  CREEN_HEIGHT ;HEIGHT OF DISPLAY SCREEN
              BAUD   DB   ?            ;BAUD RATE, COMPUTER TO MODEM

                                       ;the follow are extensions

              NEWBAUD     DB           ?    ;new baud rate location
              PORTSET     DB           ?    ;complete port data settings
              OVERRUN     DW           ?    ;number overruns this session

         The IDENT string is null-terminated, and does not contain a new-
         line.  The BAUD field contains the bits that Function 00h would use
         to set the port speed and data format.

         The fields related to a particular port (buffer size, space left in
         the buffer, baud rate) will be undefined if the port is not active.
         In some cases X00 can not accurately return information.  For
         example, the user can lock the baud rate at 115200 when loading
         X00.  There is no correct FOSSIL value that X00 can return in the
         BAUD field.  X00 will set the BAUD field equal to the last baud
         rate that the application attempted to set, at least that's what
         X00REF.DOC says.  It has been discovered that this is not true, and
         that most the time, the BAUD field contains no usable data.

         ONEFOSsil always sets the BAUD parameter to the closest possible
         value.  FHSLink really likes this practice, and as such displays a
         baud rate without using the -B parameter.  ONEFOSsil also uses the
         NEWBAUD and PORTSET bytes.  PORTSET is the bits function 1Eh would
         write to the Line Control Register (minus the break bit).  The
         NEWBAUD byte contains a value similar to what function 1Eh would
         use to set the baud rate.  These are shown below.

         Values of NEWBAUD:

                00h = 110    27% error factor on 8250 series
                01h = 150
                02h = 300
                03h = 600
                04h = 1200
                05h = 2400
                06h = 4800
                07h = 9600
                08h = 19200
                09h = 28800
                0Ah = 38400
                0Bh = 57600
                0Ch = 76800  does not exist on 8250 series
                0Dh = 115200

         Values of PORTSET:

              Bit 7 and 6 are always clear

              Bit 3 is set if parity is enabled

              Bits 5 - 4 define parity:

                   00 = Odd parity
                   01 = Even parity
                   10 = Mark parity (sticky odd)
                   11 = Space parity (sticky even)

              Bit 2 defines the number of stop bits transmitted

                   0 = 1 stop bit sent
                   1 = 1.5 stop bits for 5 bit bytes, 2 for all others

              Bits 1 - 0 define the number of data bits

                   00 = 5 data bits
                   01 = 6 data bits
                   10 = 7 data bits
                   11 = 8 data bits

         The OVERRUN word is solely for information.

    Extended Functions

    Function numbers above 1Bh and below 7Eh are X00 extended functions.
    These functions will only work with X00 and ONEFOSsil.  It is fairly
    easy to see if other FOSSIL's support X00 functions by checking the
    maximum function supported on the "Activate" call.

    It is the hope of Ray Gwinn that these functions will be added by other
    FOSSIL authors in their implementations and become a part of the FOSSIL
    specification.  I would personally like to see a whole new, non UART
    specific specification emerge.  This new specification would get rid of
    the inefficiency FOSSIL 5 permits and clear up some of the compatibility
    issues with the new BIOS's.

    Functions 1Ch and 1Dh are exact duplicates of FOSSIL functions 04h and
    05h.  Functions 1Eh and 1Fh are intended to be exact duplicates of
    functions 04h and 05h of the PS/2's BIOS INT 14h.  Function 20h is a
    destructive read with no wait.  Function 21h is a Stuff/Poke character
    into the receive buffer.  Note that function 1Eh or 1Fh are not exactly
    compatible with functions 04h and 05h of the PS/2 BIOS.

    Developers are encouraged start using functions 1Ch and 1Dh instead of
    functions 04h and 05h.  See the application notes section for
    instructions on a compatible method of determining if functions 1Ch and
    1Dh should be used instead of functions 04h and 05h.

    Function 1Ch - Activate Port.

         This function is identical to function 04h.  Please refer to
         function 04h for information.

    Function 1Dh - Deactivate Port.

         This function is identical to function 05h.  Please refer to
         function 05h for information.

    Function 1Eh - Extended line control initialization.

         This function is intended to exactly emulate the PS/2's BIOS INT 14
         services, function 04h.  Some or all of the functions provided here
         are duplicated by other FOSSIL functions.  In addition, once this
         function is called, function 00h will not be allowed to change the
         baud rate.  Function 00h will again be allowed to set the baud rate
         after the FOSSIL functions have been deactivated.

         Input: AH = 1Eh
                AL = Break, Where:
                   = 00h, No break and/or turn off break
                   = 01h, Start send of break.
                BH = Parity, where:
                   = 00h, No parity
                   = 01h, Odd parity
                   = 02h, Even parity
                   = 03h, Mark parity (always 1)
                   = 04h, Space parity (always 0)
                BL = Stop bits, where:
                   = 00h, One bit
                   = 01h, 1.5 bits on 5 bit bytes, 2 stop bits for all
         others
                CH = Word length, where:
                   = 00h, 5 bits
                   = 01h, 6 bits
                   = 02h, 7 bits
                   = 03h, 8 bits
                CL = Baud rate, where:
                   = 00h, 110 baud
                   = 01h, 150 baud
                   = 02h, 300 baud
                   = 03h, 600 baud
                   = 04h, 1200 baud
                   = 05h, 2400 baud
                   = 06h, 4800 baud
                   = 07h, 9600 baud
                   = 08h, 19200 baud
                   = 80h, 28800 baud (these are FOSSIL only baud rates)
                   = 81h, 38400 baud
                   = 82h, 57600 baud
                   = 83h, reserved (future 76800 baud)
                   = 84h, 115200 baud
                DX = Port number

         Output:   AX = Port status (see function 03h)

         If settings were locked at load time, the appropriate parameters
         are ignored.

         ONEFOSsil does not permit the break bit to be set by this function.
         The value in AL is ignored.  The reason is that the PS/2
         specification calls for a value of 0 to make a break and a 1 to
         clear a break.  X00REF.DOC states the function as it appear above,
         but the Interrupt shows it as being an exact duplicate of the PS/2
         function.  I do not wish to trouble myself with programs that fail
         to work because their authors used the Interrupt List to write
         them.

    Function 1Fh - Extended serial port status/control.

         This function is intended to exactly emulate the PS/2's BIOS INT 14
         services, function 05h.  Some or all of the functions provided here
         are duplicated by other FOSSIL functions.  This function has 2 sub-
         functions specified by AL.

         Sub-function 00h - Read MCR

         Input: AH = 1Fh
                AL = 00h, Read modem control register (MCR)
                DX = Port number

         Output:   AX = Port status (see function 03h)
                BL = Modem control register, where:
                     Bits 7-5 = 0 (Reserved) (always 0)
                     Bit 4    = 1 Loopback mode
                     Bit 3    = 1 OUT2 (interrupts) enabled
                     Bit 2    = 1 OUT1 active
                     Bit 1    = 1 Request to send (RTS) active
                     Bit 0    = 1 Data terminal ready (DTR) active

         Sub-function 01h - Write MCR

         Input: AH = 1Fh
                AL = 01h, Write modem control register (MCR)
                BL = Modem control register, where:
                     Bits 7-5 = 0 (Reserved) (forced 0)
                     Bit 4    = 1 Set loopback mode
                     Bit 3    = 1 Set OUT2 enable interrupts (forced 1)
                     Bit 2    = 1 Set OUT1 active (on)
                     Bit 1    = 1 Set Request to send active (on)
                     Bit 0    = 1 Set DTR active (on)
                DX = Port number

         Output:   AX = Port status (see function 03h)

         In sub-function 01h (write MCR) X00 will force bit 3 to 1.  That
         is, X00 will not allow the communications interrupts to be
         disabled.

         RTS may be used as a flow control signal by the FOSSIL.  When
         the application program writes the MCR, the RTS bit is treated as
         an RTS enable bit.  This means that X00 will allow the application
         program to signal when it wants to allow RTS on.  It does not force
         RTS on.

         RTS only permits the DTR to be modified with this function.  This
         function should not be used for any reason.  It is hardware
         specific and such hardware may not exist in the future.

    Function 20h - Read with no wait (destructive).

         Input: AH = 20h
                DX = Port number

         Output:   AH = 00h if a character is available
                   > 00h if no character is available
                AL = Next character if available

         This function returns the next character from the receive buffer.
         This function is the same as function 0Ch except that any character
         returned is removed from the receive buffer.

    Function 21h - Stuff/Poke the receive buffer.

         Input: AH = 20h
                AL = Character to place in the receive buffer
                DX = Port number

         Output:   Nothing

         This function will insert the passed character into the receive
         buffer (at the end).  Subsequent reading of the serial input will
         read the character.  The character is inserted at the end of the
         buffer (as though it were just received.)

         The character is inserted into the receive buffer by calling the
         receive interrupt routine.  All normal receive checking is
         preformed on the character.  Some things to note are:

              If receiving of Xon/Xoff is enabled and an Xoff is
              stuffed/poked into the buffer, the transmitter will stop
              until a an Xon is received or stuffed/poked.

              If Control-C/K checking is enabled and a Control-C/K is
              stuffed/poked, then the character is not put in the
              buffer and the internal flag is set.

         ONEFOSsil does not support this function as there is no known need
         for it.

                         "Layered Application" services

    ONEFOSsil supports NO "Layered Application" services.  The functions
    simply aren't monitored.  I don't feel most people have any use for
    them.

                               Application Notes

                   Which Activate/Deactivate functions to use

    It is the hope of Ray Gwinn (after a period of time) to make X00's
    functions 04h and 05h compatible with the PS/2's INT 14h functions 04h
    and 05h.  Currently, X00's functions 04h and 05h are duplicated at
    functions 1Ch and 1Dh respectively.  Ray requests that application
    programmers start using functions 1Ch and 1Dh if those functions are
    available.  That is, use functions 1Ch and 1Dh instead of functions 04h
    and 05h respectively.

    It is relatively simple to determine if the functions at 1Ch and 1Dh are
    available.  When your program is ready to activate the FOSSIL for a
    given port, issue function 1Ch.  If 1954h is returned, then the port is
    activated.  If 1954h is not returned, reissue the request to function
    04h.  Save the function number actually used to activate the port, then
    increment it by one to deactivate the port.  You may also keep track of
    the maximum function supported by the driver, to see what other calls
    are available.  You should; however, leave a user configured option to
    override all extended function calls.

    <EoF>
