+\begin_layout Standard
+0000-7FFF
+\end_layout
+
+\end_inset
+</cell>
+<cell alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+common
+\end_layout
+
+\end_inset
+</cell>
+<cell multicolumn="1" alignment="center" valignment="top" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+
+\end_layout
+
+\end_inset
+</cell>
+<cell multicolumn="2" alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+
+\end_layout
+
+\end_inset
+</cell>
+</row>
+<row>
+<cell multicolumn="1" alignment="center" valignment="top" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+SiLabs C8051F120 example
+\end_layout
+
+\end_inset
+</cell>
+<cell multicolumn="2" alignment="center" valignment="top" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+
+\end_layout
+
+\end_inset
+</cell>
+<cell multicolumn="2" alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+
+\end_layout
+
+\end_inset
+</cell>
+<cell multicolumn="2" alignment="center" valignment="top" topline="true" leftline="true" usebox="none">
+\begin_inset Text
+
+\begin_layout Standard
+
+\end_layout
+
+\end_inset
+</cell>
+</row>
+</lyxtabular>
+
+\end_inset
+
+
+\newline
+
+\newline
+Usually the hardware uses some sfr (an output port or an internal sfr) to
+ select a bank and put it in the banked area of the memory map.
+ The selected bank usually becomes active immediately upon assignment to
+ this sfr and when running inside a bank it will switch out this code it
+ is currently running.
+ Therefor you cannot jump or call directly from one bank to another and
+ need to use a so-called trampoline in the common area.
+ For SDCC an example trampoline is in crtbank.asm and you may need to change
+ it to your 8051 derivative or schematic.
+ The presented code is written for the C8051F120.
+\newline
+
+\newline
+When calling a banked function
+ SDCC will put the LSB of the functions address in register R0, the MSB
+ in R1 and the bank in R2 and then call this trampoline
+\emph on
+__sdcc_banked_call
+\emph default
+.
+ The current selected bank is saved on the stack, the new bank is selected
+ and an indirect jump is made.
+ When the banked function returns it jumps to
+\emph on
+__sdcc_banked_ret
+\emph default
+ which restores the previous bank and returns to the caller.
+\end_layout
+
+\begin_layout Subsubsection
+Software
+\end_layout
+
+\begin_layout Standard
+When writing banked software using SDCC you need to use some special keywords
+ and options.
+ You also need to take over a bit of work from the linker.
+\newline
+
+\newline
+To create a function
+ that can be called from another bank it requires the keyword
+\emph on
+banked
+\emph default
+
+\begin_inset LatexCommand index
+name "banked"
+
+\end_inset
+
+.
+ The caller must see this in the prototype of the callee and the callee
+ needs it for a proper return.
+ Called functions within the same bank as the caller do not need the
+\emph on
+banked
+\emph default
+ keyword nor do functions in the common area.
+ Beware: SDCC does not know or check if functions are in the same bank.
+ This is your responsibility!
+\newline
+
+\newline
+Normally all functions you write end up in
+ the segment CSEG.
+ If you want a function explicitly to reside in the common area put it in
+ segment HOME.
+ This applies for instance to interrupt service routines as they should
+ not be banked.
+\end_layout
+
+\begin_layout Standard
+Functions that need to be in a switched bank must be put in a named segment.
+ The name can be mostly anything up to eight characters (e.g.
+ BANK1).
+ To do this you either use -
+\begin_inset ERT
+status collapsed
+
+\begin_layout Standard
+
+
+\backslash
+/
+\end_layout
+
+\end_inset
+
+-codeseg BANK1 (See
+\begin_inset LatexCommand ref
+reference "lyx:-codeseg"
+
+\end_inset
+
+) on the command line when compiling or #pragma codeseg BANK1 (See
+\begin_inset LatexCommand ref
+reference "sec:Pragmas"
+
+\end_inset
+
+) at the top of the C source file.
+ The segment name always applies to the whole source file and generated
+ object so functions for different banks need to be defined in different
+ source files.
+\newline
+
+\newline
+When linking your objects you need to tell the linker where
+ to put your segments.
+ To do this you use the following command line option to SDCC: -Wl-b BANK1=0x180
+00 (See
+\begin_inset LatexCommand ref
+reference "lyx:-Wl option"
+
+\end_inset
+
+).
+ This sets the virtual start address of this segment.
+ It sets the banknumber to 0x01 and maps the bank to 0x8000 and up.
+ The linker will not check for overflows, again this is your responsibility.
+\end_layout
+
+\begin_layout Standard
+\begin_inset VSpace bigskip
+\end_inset
+
+
+\end_layout
+
+\begin_layout Section
+DS400 port
+\end_layout
+
+\begin_layout Standard
+The DS80C400
+\begin_inset LatexCommand index
+name "DS80C400"
+
+\end_inset
+
+
+\begin_inset LatexCommand index
+name "DS400"
+
+\end_inset
+
+ microcontroller has a rich set of peripherals.
+ In its built-in ROM library it includes functions to access some of the
+ features, among them is a TCP stack with IP4 and IP6 support.
+ Library headers (currently in beta status) and other files are provided
+ at
+\size footnotesize
+
+\begin_inset LatexCommand url
+target "ftp://ftp.dalsemi.com/pub/tini/ds80c400/c_libraries/sdcc/index.html"
+
+\end_inset
+
+.
+
+\begin_inset VSpace bigskip
+\end_inset
+
+
+\end_layout
+
+\begin_layout Section
+The Z80 and gbz80 port
+\end_layout
+
+\begin_layout Standard
+SDCC can target both the Zilog Z80
+\begin_inset LatexCommand index
+name "Z80"
+
+\end_inset
+
+ and the Nintendo Gameboy's Z80-like gbz80
+\begin_inset LatexCommand index
+name "gbz80 (GameBoy Z80)"