Re: [Sdcc-user] mcs51 bankswitching, does anyone have it working based on crtbank.asm example trampoline?

[Maarten B. <sou...@ds...>]

Hi Anthony,

It seems bankswitching is broken. And you also found why 
already: the startup routine should be at 0x0000 and 
__sdcc_banked_call at some higher address. Does it help 
if you put the .rel which contains main() as the first 
object to link?

Programmers that cannot handle unsorted hex-files are 
too restrictive. There is nothing about sorting in the 
definition of the standard.

Parameter passing should be taken care of correctly.

Sorry for the late reply. I had a busy weekend.
Maarten

> Based on the lack of responses, and the branches of sdcc with 
> modifications to fix bank switching, I believe the banking in the 
> official version is broken.  The documentation should be updated to 
> indicate this so future users don't waste their time trying to use it.
> 
> The branched version are not keeping up with the latest sdcc releases, 
> they only support 2.7.0 and 2.8.0.
> 
> If you are curious you should look at this sdcc branch, modified "with 
> banking"
> 
> http://sourceforge.net/projects/ccflasher/files/
> 
> 
> If there is any way to make the bank switching work in the mainline 
> code, I am willing to help test and document it.
> 
> 
> Anthony
> 
> 
> 
> Anthony Asterisk wrote:
> > Hello SDCC-users,
> >
> >   From reading the sdcc documentation, bank switching for the mcs51 is 
> > supported through the sdcc specific keyword __banked, a codeseg 
> > command line switch (or inline pragma) and the trampoline calls 
> > __sdcc_banked_call  and __sdcc_banked_ret.  The cc2430 chip that I am 
> > using provides a bank switching SFR called FMAP that is functionally 
> > similar to the crtbank.asm examples PSBANK, therefore I expect the 
> > crtbank.asm trampoline should work with no changes.  However when I 
> > mark any routine as banked, even if it is in the HOME bank, the code 
> > does not work...
> > Changes that I notice when using banking:
> >
> > The trampoline functions get added to final map file (demo.map)
> >
> > Area                               Addr   Size   Decimal Bytes 
> > (Attributes)
> > --------------------------------   ----   ----   ------- ----- 
> > ------------
> > HOME                               0000   00AC =    172. bytes 
> > (REL,CON,CODE)
> >
> >       Value  Global
> >    --------  --------------------------------
> >   0C:0000    __sdcc_banked_call
> >   0C:0016    __sdcc_banked_ret
> >   0C:009F    __sdcc_program_startup
> >   0C:00A4    __sdcc_call_dptr
> >   0C:00A6    _hello_world
> >
> >
> > ** Is the location of __sdcc_banked_call at address 0000 in the HOME 
> > segment a problem?  I expected the start up routines would normally go 
> > at 0000.
> >
> > ** From discussions with some other users of the cc2430/sdcc, it seems 
> > the banked mode does not work as described in the documentation.  
> > Specifically, I have been informed of some undocumented requirements...
> >   - generated hex file is in an unusual format that is not compatible 
> > with "commercial" programmers and must converted somehow
> >   - all code must be assigned to a bank, it will not work if any code 
> > is unassigned
> >   - all banks must have some code assigned to it
> >
> >
> > ** Does anyone have the documented approach to bank switching 
> > working?  Is there some source code online that I can study?
> >
> > ** If the documented method does not work, I would be willing to help 
> > update the documentation if someone can explain the current  
> > requirements and implementation.
> >
> >
> > Here are the bank switching assembly routines...
> >
> >        .area HOME    (CODE)
> >
> > __sdcc_banked_call::
> >         push    _PSBANK         ;save return bank
> >         xch     a,r0            ;save Acc in r0, do not assume any 
> > register bank
> >         push    acc             ;push LSB address
> >         mov     a,r1
> >         push    acc             ;push MSB address
> >         mov     a,r2            ;get new bank
> >         anl     a,#0x0F         ;remove storage class indicator
> >         anl     _PSBANK,#0xF0
> >         orl     _PSBANK,a       ;select bank
> >         xch     a,r0            ;restore Acc
> >         ret                     ;make the call
> >
> > __sdcc_banked_ret::
> >         pop     _PSBANK         ;restore bank
> >         ret                     ;return to caller
> >
> >
> > Generated assembly code for a banked call:
> >
> > ;       demo.c:82: abc=hello_world();
> >         mov     r0,#_hello_world
> >         mov     r1,#(_hello_world >> 8)
> >         mov     r2,#(_hello_world >> 16)
> >         lcall   __sdcc_banked_call
> >         mov     r2,dpl
> >         mov     r3,dph
> >
> >
> >
> > ;       hello_world.c:15: return 123;
> >         mov     dptr,#0x007B
> >         ljmp    __sdcc_banked_ret
> >
> >
> > Questions:
> >
> >   - the parameters passed on the stack to banked routine would come 
> > before _PSBANK.  Will the banked routine skip over the stored _PSBANK 
> > to reach them?  So far I have only attempted to routines without 
> > parameters. 
> 
> 
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