\size footnotesize
\newline
-$Date:: $
+$Date:: $
\newline
$Revision$
\end_layout
\end_inset
+\begin_inset LatexCommand \label{lyx:-Wl option}
+
+\end_inset
+
...
Pass the linkOption to the linker.
If a bootloader is used an option like
\end_inset
would be typical to set the start of the code segment.
+ Either use the double quotes around this option or use no space (e.g.
+ -Wl-bCSEG=0x1000).
See also #pragma constseg and #pragma codeseg in section
\begin_inset LatexCommand \ref{sec:Pragmas}
\end_inset
+\begin_inset LatexCommand \label{lyx:-codeseg}
+
+\end_inset
+
\InsetSpace ~
<Name> The name to be used for the code
\begin_inset LatexCommand \index{code}
\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.
- Because the selected bank usually becomes active immediately you cannot
- jump call directly from one bank to another and need to use a so-called
- trampoline in the common area.
+ 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
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 __sdcc_banked_call.
+ 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 __sdcc_banked_ret which restores
- the previous bank and returns to the caller.
+ 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
\newline
To create a function
- that can be called from another bank it requires the keyword banked.
+ that can be called from another bank it requires the keyword
+\emph on
+banked
+\emph default
+
+\begin_inset LatexCommand \index{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 banked
+ 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!
Functions that need to be in a switched bank must be put in a named segment.
The name can be mostly anything upto eight characters (e.g.
BANK1).
- To do this you either use --codeseg BANK1 on the command line when compiling
- or #pragma codeseg BANK1 at the top of the C source file.
+ 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{lyx:-codeseg}
+
+\end_inset
+
+) on the command line when compiling or #pragma codeseg BANK1 (See
+\begin_inset LatexCommand \ref{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.
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.
+00 (See
+\begin_inset LatexCommand \ref{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.
projects / fw / sdcc / commitdiff