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# apple1-videocard-lib # apple1-videocard-lib
Library and demos for the "Apple-1 Graphic Card" by P-LAB, Library and demos for the "Apple-1 Graphic Card" by P-LAB,
featuring the TMS9918 Video Display Processo by Texas Instruments. featuring the TMS9918 Video Display Processor by Texas Instruments.
## Repo structure ## Repo structure
``` ```
demo a demo program that makes use of the library demo/ a demo program that makes use of the library
docs TMS9918 and Apple1 manuals docs/ TMS9918 and Apple-1 manuals
kickc target configuration files for KickC kickc/ target configuration files for KickC
lib the library files to include in your project lib/ the library files to include in your project
tetris a demo game tetris/ a demo game
tools some build tools tools/ some build tools
``` ```
## Introduction ## Introduction
@ -22,12 +22,11 @@ with the "Apple-1 Graphic Card" board by [P-LAB]() or any
other video card that maps the TMS9918 in the `$CC00`-`$CC01` other video card that maps the TMS9918 in the `$CC00`-`$CC01`
memory range of the Apple-1. memory range of the Apple-1.
The library is written in C with [KickC](https://gitlab.com/camelot/kickc/-/releases) The library is written in C with [KickC](https://gitlab.com/camelot/kickc/-/releases), a very efficient 6502 C compiler.
which is a very efficient 6502 C compiler.
## Choice of the screen mode ## Choice of the screen mode
The library only supports screen modes 1 and 2 (screen 0 and screen 3 not The library supports screen modes 1 and 2 only (screen 0 and screen 3 not
being very useful). Both are 256x192 pixels but there are some differences being very useful). Both are 256x192 pixels but there are some differences
you should consider when evaluating which mode to use: you should consider when evaluating which mode to use:
@ -115,7 +114,7 @@ screen2_puts(16, 12, col, "HELLO");
Some example code: Some example code:
```c ```c
// writes the value 42 at the VRAM location 8000 // writes the value 42 at VRAM location 8000
tms_set_vram_write_addr(8000); tms_set_vram_write_addr(8000);
TMS_WRITE_DATA_PORT(42); TMS_WRITE_DATA_PORT(42);
@ -125,7 +124,7 @@ byte val = TMS_READ_DATA_PORT;
``` ```
When using the default values that came with `SCREEN1_TABLE[]` and `SCREEN2_TABLE[]`, When using the default values that came with `SCREEN1_TABLE[]` and `SCREEN2_TABLE[]`,
the VRAM is organized according the following memory map: VRAM is organized according the following memory map:
```c ```c
// ZONE RANGE NAME YOU CAN USE IN C // ZONE RANGE NAME YOU CAN USE IN C
// =========================================================== // ===========================================================
@ -200,35 +199,35 @@ from the `lib/` directory in your C source files.
Compile your sources with the KickC compiler, the `tools/` Compile your sources with the KickC compiler, the `tools/`
directory contains a `build.bat` script example for Windows. directory contains a `build.bat` script example for Windows.
There are three configurations you can target with the KickC There are three configurations you can target with the switches `-t target -targetdir thisrepopath/kickc` of the KickC compiler:
compiler switches `-t target -targetdir thisrepopath/kickc`:
- apple1 - `apple1`
- apple1_jukebox - `apple1_jukebox`
- vic20 - `vic20`
#### Target "apple1" #### Target "apple1"
With this target, the compiled program will start at `$280` in With this target, the compiled program will start at `$0280` in
the free RAM on the Apple-1 (please make sure you have enough RAM). the free RAM of the Apple-1 (please make sure you have enough RAM).
TODO: add reference to `hexdump.js` (TODO: add reference to `hexdump.js`)
#### Target "apple1_jukebox" #### Target "apple1_jukebox"
This target is for expansion Cards that provide a ROM storage in This target is for expansion cards that provide a ROM storage in
the range `$4000`-`$7FFF`, as: the range `$4000`-`$7FFF`, as:
- the "CodeTank" EEPROM daughterboard of the "Apple-1 Graphic Card" - the "CodeTank" EEPROM daughterboard of the "Apple-1 Graphic Card"
- "Juke-Box Card" FLASH - "Juke-Box Card" FLASH
In this target configuration, the program is split into two segments: In this target configuration, the program is split into two segments:
- the "Code" that resides in ROM at `$4000` - the `Code` that resides in ROM at `$4000`
- the "Data" that resides in RAM at `$0280` - the `Data` that resides in RAM at `$0280`
(this because the program needs to change the "Data").
The split is required because the program needs to write on the `Data` segment (e.g. when changing the value of a variable).
The only issue is that the "Data" segment needs to be initialized The only issue is that the "Data" segment needs to be initialized
with the startup values (for example, the value that a global `int` variable with the correct startup values (for example, the value that
takes before it's used). a global `int` variable takes before it's used).
The "Data" initialization needs to be done manually in the C program The "Data" initialization needs to be done manually in the C program
by explicitly calling `apple1_eprom_init()` in `main()`. The function by explicitly calling `apple1_eprom_init()` in `main()`. The function