crossbow-7800

File: README.DOC

ATARI 7800 CROSSBOW

Notes for final release

6/29/88

Scott Marshall


The disks contain the final relese of ATARI 7800 CROSSBOW, which
includes all source and batch files for code maintainence.

Directories and Files:

\C Main Crossbow directory
\C\BM Bitmap files, switch banks, and the lower fixed bank

\C\C.S Code for upper fixed bank ($C000 .. $FFFF)
\C\TABLES.S Tables for upper fixed bank
\C\EQUATES.S Constants
\C\VARS.S Variables
\C\MACROS.S Macros
\C\COLDET.S Collision detection code
\C\AUDEQU.S Audio equates

\C\MAKE.S Maintainence batch files
\C\ASSEMBLE.S
\C\DOWNLOAD.S

\C\BM\M*.BAT Batch file to make each bank
\C\BM\MAKE.BAT Batch file to make all banks in \C\BM

\C\ADDR.S Equates to set global addresses

\C\BM\BD*.S Bank data, 0 .. 6 ($8000 .. $BFFF)

\C\BM\*.S Graphics and data tables

\C\BM\BDF.S Lower fixed bank ($4000 .. $7FFF)

\INCLUDE\MARIA.S 7800 includes.

The lower fixed bank contains:

Grahics common to many crossbow screens.
Audio tables
Collision detection lookup table
Cave bat flying animation sequence (overflow from upper fixed bank)
Light gun code (currently a dummy subroutine)

NOTES ON LIGHT GUN CODE:

I wrote a dummy light gun subroutine in the source file \C\BM\BDF.S.
It is named "DOGUN", and 512 bytes are available for it. If the player selects
"gun" instead of "stick", this subroutine is called during every vertical
blanking period while a game board is active. If there is no firing, it
should return zero, and non-zero if the gun has been fired. On firing, x and y
positions should be written to the variables "movx+N_CURSOR" and
"movy+N_CURSOR", with a fudge factor of 5 units subtracted from each to center
the graphic "splotch". The routine should test the bit "S_STOPPED" in the byte
"movsta+N_CURSOR" before allowing a fire. If this bit is high, it means that
the fire sequence is still running, and subsequent firing should be prevented
until this bit clears. Samples of all of this are working and commented in
the dummy routine.

To modify and test this routine, run the batch file "\C\BM\MF.BAT",
return to the directory "\C" and run "DOWNLOAD.BAT".


Any questions, I can be reached at 1-609-443-6617.

Yours Truly,
Scott Marshall