diff --git a/doc/atari5200.sgml b/doc/atari5200.sgml index 325602b37..cbddbd928 100644 --- a/doc/atari5200.sgml +++ b/doc/atari5200.sgml @@ -5,7 +5,7 @@ Atari 5200 specific information for cc65 <author> <url url="mailto:chris@groessler.org" name="Christian Groessler"><newline> -<date>2014-05-15 +<date>2014-05-27 <abstract> An overview over the Atari 5200 runtime system as it is implemented for the @@ -39,18 +39,29 @@ config. <sect>Memory layout<p> -cc65 generated programs with the default setup run with the I/O area and a -CHR bank enabled, which gives a usable memory range of $8000 - $FFF3. -All boot ROM entry points may be called directly without additional code. +cc65 generated programs with the default setup use the RAM space from $021C to +$3FFF. If you want to reserve memory for the display list and screen buffer +you should define the __RESERVED_MEMORY__ linker variable. The number +of bytes specified by __RESERVED_MEMORY__ are lowering the top of +memory, therefore the available +RAM memory for the program is $021C to $3FFF-__RESERVED_MEMORY__. +The default linker config file sets __RESERVED_MEMORY__ to $1E0 +to reserve space for an optional CONIO text screen. Special locations: <descrip> <tag/Text screen/ - The text screen is located at VRAM $2000. + The text screen is only enabled if any of the CONIO output routines + is used in the program. Its size is 20x24 characters (Antic mode 6, + BASIC mode 1). The text screen is located at $3E00. The + address of the screen memory is available at runtime in the variable + SAVMSC ($001B).<p> + If the program doesn't use any CONIO output functions it needs to setup its own + display list. <tag/Stack/ - The C runtime stack is located at $7FFF and growing downwards. + The C runtime stack is located at $3FFF-__RESERVED_MEMORY__ and growing downwards. <tag/Heap/ The C heap is located at the end of the program and grows towards the C @@ -68,31 +79,43 @@ Programs containing Atari 5200 specific code may use the <tt/atari5200.h/ header <sect1>Atari 5200 specific functions<p> <itemize> -<item>??? +<item>TBD. </itemize> <sect1>Hardware access<p> -The following pseudo variables declared in the <tt/nes.inc/ include file do -allow access to hardware located in the address space. +The following pseudo variables declared in the <tt/atari5200.h/ header +file do allow access to hardware located in the address space. Some +variables are structures, accessing the struct fields will access the +chip registers. <descrip> - <tag><tt/PPU/</tag> - The <tt/PPU/ defines allow access to the PPU chip. + <tag><tt/GTIA_READ/ and <tt/GTIA_WRITE/</tag> + The <tt/GTIA_READ/ structure allows read access to the GTIA. The + <tt/GTIA_WRITE/ structure allows write access to the GTIA. + See the <tt/_gtia.h/ header file located in the include directory + for the declaration of the structure. - <tag><tt/APU/</tag> - The <tt/APU/ defines allow access to the APU chip. + <tag><tt/POKEY_READ/ and <tt/POKEY_WRITE/</tag> + The <tt/POKEY_READ/ structure allows read access to the POKEY. The + <tt/POKEY_WRITE/ structure allows write access to the POKEY. + See the <tt/_pokey.h/ header file located in the include directory + for the declaration of the structure. + + <tag><tt/ANTIC/</tag> + The <tt/ANTIC/ structure allows read access to the ANTIC. + See the <tt/_antic.h/ header file located in the include directory + for the declaration of the structure. </descrip><p> - <sect>Loadable drivers<p> -All drivers must be statically linked because no file I/O is available. +All drivers must be statically linked because no disk I/O is available. The names in the parentheses denote the symbols to be used for static linking of the drivers. @@ -135,11 +158,8 @@ No serial drivers are available for the Atari 5200. <sect1>Disk I/O<p> -The existing library for the Atari 5200 doesn't implement C file -I/O. There are no hacks for the <tt/read()/ and <tt/write()/ routines. - -To be more concrete, this limitation means that you cannot use any of the -following functions (and a few others): +Disk I/O is not supported by the <tt/atari5200/ target. This means that +you cannot use any of the following functions (and a few others): <itemize> <item>fclose