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1988-02-11
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Fundamentals of FOSSIL implementation and use
Version 5, February 11, 1988
Rick Moore, Solar Wind Computing
FidoNet Address: Zone 1, Network 115, Node 333 (1:115/333)
Copyright (C) 1987, VEP Software, Naugatuck, CT 06770. All rights reserved.
Copyright (C) 1988, Rick Moore, Homewood, IL, 60430. All rights reserved.
This document may be freely used or copied by anyone interested in the data
contained herein. No fees may be charged for distribution of this document.
You will be held accountable for all such charges, and expected to either
reimburse those persons or organizations so charged, or to make a donation
in the exact amount of those fees to the International FidoNet Association,
to assist them in their efforts to advance the technology of personal
computer telecommunications.
Fundamentals of FOSSIL implementation and use Page 2
Introduction
A. Objectives of this document
This document is directed at implementors or intellectuals. It is meant
for use in implementing applications that can use FOSSIL drivers, or for
details needed to implement a new FOSSIL. As such it won't always go out
of its way to explain itself to the neophyte.
This document will have served its purpose to you if you are able to use
the data contained within to perform either of the above tasks. If you
feel that necessary data has been omitted please contact Rick Moore
at the above listed address so that the appropriate changes can be made.
Any lines changed in the current version are marked with "|" in the left
margin.
B. Historical perspective
For those people who were not lucky enough to have an IBM PC or a system
nearly completely compatible, the world has not been very friendly. With
his implementation of the Generic Fido(tm) driver, Tom Jennings made it
possible for systems that had nothing in common with an IBM PC except an
808x-class processor, and the ability to run MS-DOS Version 2 and above,
to run his Fido(tm) software. That was a lot to ask, and a lot of people
thought it was enough.
But not everyone. While Thom Henderson was debugging Version 4.0 of his
SEAdog(tm) mail package, an "extended" Generic driver was designed (in
cooperation with Bob Hartman) as a quick kludge to help him get past a
problem with certain UART chips.The new hook was quickly pounced upon by
Vince Perriello, who, with almost DAILY prodding (ouch! it still hurts)
by Ken Kaplan,had been working with Henderson to get DEC Rainbow support
into SEAdog. Vince then coded a driver to use this hook and - Voila! -
SEAdog 4.0 started working like a champ on the Rainbow.
At the same time something was rotten in the state of Texas. Wynn Wagner
started encountering some serious difficulties in his Opus development
effort. Specifically, he couldn't force the Greenleaf(tm) Communications
Libraries to behave in exactly the way he felt Opus required. Enter Bob
Hartman.Having already enjoyed success in the effort with Thom Henderson,
he suggested to Wynn that with very few extensions, any driver that was
already SEAdog(tm) 4.0 compatible could drive Opus as well. About that
time, Vince called Wynn to discuss porting Opus to the DEC Rainbow. Wynn
called Bob, Bob called Vince, and the FOSSIL driver came into existence.
FOSSIL is an acronym for "Fido/Opus/SEAdog Standard Interface Layer". To
say that the concept has gained wide acceptance in the FidoNet community
would be an understatement. Henk Wevers' DUTCHIE package uses the FOSSIL
communications services. Ron Bemis' OUTER package uses FOSSIL services
for everything it does and as a result it is completely generic. There
are already FOSSIL implementations for the Tandy 2000, Heath/Zenith 100,
Sanyo 555 and other "non-IBM" architectures. With each new 'port' of the
spec, the potential of a properly coded FOSSIL application grows!
Fundamentals of FOSSIL implementation and use Page 3
Basic conventions and calling method
C. Basic principles of a FOSSIL driver
1) Interrupt 14h.
The one basic rule that the driver depends upon, is the ability for ANY
target machine to allow the vector for INT 14h (usually pointing to BIOS
comm functions) to be "stolen" by the driver. In a system where the INT
14h vector is used already, it must be possible to replace the "builtin"
functionality with that of a FOSSIL, when an application that wants the
use of a FOSSIL is to be run on the target machine.
2) How to install a FOSSIL driver in a system
There's no hard and fast way to do this. The FOSSIL might be implemented
as part of a device driver (like Ray Gwinn's X00.SYS) and therefore gets
loaded using a line in CONFIG.SYS at bootup time. It might be done as a
TSR (terminate and stay resident) program, in which event you install it
by running the program (DECcomm by Vince Perriello and Opus!Comm by Bob
Hartman work this way, for example).
3) How an application can detect the presence of a FOSSIL
The driver has a "signature" that can be used to determine whether it is
present in memory. At offset 6 in the INT 14h service routine is a word,
1954h, followed by a byte that specifies the maximum function number
supported by the driver. This is to make it possible to determine when a
driver is present and what level of functionality it provides. Also, the
Init call (see below) returns a 1954h in AX. SEAdog(tm) looks at the
signature and Opus just goes for the Init. Fido doesn't do either.
4) How to call a FOSSIL function
The FOSSIL driver is entered by issuing a software Interrupt 14h from
the application program. The code corresponding to the desired function
should be in 8-bit register AH. For calls that relate to communications,
the port number will be passed from the application in register DX. When
DX contains a zero (0) it signifies use of COM1, or whatever the "first"
serial port on your machine is called. A one (1) in DX points the driver
at COM2, and so on. A value of 00FFh in DX is considered a special case
where the driver should do no actual processing but return SUCCESS. In
the specific case of Init/Uninit with DX=00FFh,the FOSSIL should perform
all non-communications processing necessary with such calls. In some
machines (H/Z-100 for example), the FOSSIL must assume control of the
keyboard in order to service the keyboard functions.
FOR ALL FUNCTIONS, ALL REGISTERS NOT SPECIFICALLY CONTAINING A FUNCTION
RETURN VALUE MUST BE PRESERVED ACROSS THE CALL.
Fundamentals of FOSSIL implementation and use Page 4
Communications functions
D. Functions currently defined for FOSSILs
AH = 00h Set baud rate
Parameters:
Entry: AL = Baud rate code
DX = Port number
| Exit: AX = Port status (see function 03h)
This works the same as the equivalent IBM PC BIOS call, except that it
ONLY selects a baud rate. This is passed in the high order 3 bits of AL
as follows:
010 = 300 baud
011 = 600 ''
100 = 1200 ''
101 = 2400 ''
110 = 4800 ''
111 = 9600 ''
000 = 19200 '' (Replaces old 110 baud mask)
001 = 38400 '' (Replaces old 150 baud mask)
The low order 5 bits can be implemented or not by the FOSSIL, but in all
cases, if the low order bits of AL are 00011, the result should be that
the communications device should be set to eight da