PICPROGA - PIC programmer with support for "A" suffix PICs. 07/01/06

Copyright (C) Pigeon <pigeon@pigeon.dyndns.org> 2006. License: GPL.

PICPROGA will program both the old 16F873 and the new 16F873A PICs, plus
other PICs with compatible programming specifications such as the 12F683.

It makes use of four environment variables which should be set or unset
as required before running the program:

PICCONFW     This defines the Configuration Word (sometimes called
               "the fuses" by the ignorant) to be written to the PIC
               configuration register. This must be set according to
               the requirements of the code being programmed. For all
               TFH projects to date, it is 3F72.

PICAMODE     This selects whether the newer "A"-suffix PICs or the older
               PICs without the "A" suffix are being programmed. It should
               be set (to any value) to program "A"-suffix PICs, and
               unset to program the older versions. If it is not set
               appropriately for the PIC being programmed, huge numbers of
               programming errors will occur.

PICLPTADDR   This defines the address of the LPT port to which the PIC
               programmer is connected. In general this will be 378 for LPT1
               or 278 for LPT2. The value of 3BC is also recognised. Any
               other value will cause the program to abort.

PICDUMPMODE  This selects whether PICPROGA is programming the PIC or dumping
               the contents of the PIC to a file. It should be set (to any
               value) to dump, and unset to program.
              

PICPROGA is called using the syntax: PICPROGA <filename>
where <filename> is the name of the file containing the source code, or the
name of the file to which the contents of the PIC are to be dumped in dump
mode.

PICPROGA may be compiled for either Linux or DOS by defining the appropriate
preprocessor directive in the source code, as below:

To compile for Linux:
#define LINUX
#undef DOS

To compile for DOS:
#undef LINUX
#define DOS

When compiling for Linux, the executable must be made setuid root in order
to gain i/o permissions for the printer port.

It has been tested under gcc-2.95 for Linux, and Turbo C 3.0 for DOS.

PICPROGA is free software and may be freely distributed under the terms of
the GNU GPL.

PICPROGA requires a PIC programming adaptor connected to the parallel port
according to the following scheme:

Signal          Pin   Bit   Function
======          ===   ===   ========
Vpp control     17    C3    Turn on Vpp (negative logic)
Vpp feedback    15    S3    Report state of Vpp (positive logic)

Data out         3    D1    Data out to PIC (positive logic)
Data in         11    S7    Data return from PIC (negative logic)

Clock            2    D0    Clock signal to PIC (positive logic)
Clock feedback  12    S5    Verifies clock signal at PIC (positive logic)

"Positive logic" and "negative logic" refer to the states of the signals
at the actual pins of the printer port, ie, the programming adaptor must
invert the "Vpp control" and "Data in" signals but not the others.