[avr-gcc-list] Allocation of large globals in external RAM

[Molnar Zoltan]

Hi all,

I'm still having problems in allocating large global variables in external RAM.

How can I tell the linker that I have 32K external RAM?
How can I tell the linker where to put the stack (--defsym __stack=0x08000 
returns 'No such file or directory').

Does anybody have working makefiles for early MCUCR, stack initialization?

Here I enclose a test program and my makefile (I'm using gcc 2.97), please run 
the code and help if You can.

Thank You 
Zoltan Molnar
---
test program:
#include <io.h>
#include <interrupt.h>

#define FIFOlgth 2000

typedef unsigned char  u08;
typedef          char  s08;
typedef unsigned short u16;
typedef          short s16;
typedef u08            bool;

typedef struct {
    u16 min,max,o,f;
    bool isfull;    
    u08 data[FIFOlgth];
} t_fifo;
       

t_fifo fifo;
//******************************************
//MAIN PROGRAM
int main (void)
{
 /*set up port pin directions and levels*/
 outp(0x56,DDRB);         
 outp(0xFF,PORTB);        
 outp(0xD6,DDRD);        
 outp(0xFF,PORTD);        
 
 outp(0x80,MCUCR);        /*enable XSRAM, how to do it from linker???*/
 
 
 sei();

 fifo.min=0;
 fifo.max=FIFOlgth-1;
 fifo.o=0;
 fifo.f=0;

 for(;;)
 { }    
 return 0;      
}

makefile:

###### define some variables based on the AVR base path in $(AVR) #######
        CC=avr-gcc
        AS=avr-gcc -x assembler-with-cpp        
        RM=rm -f
        RN=mv
        BIN=avr-objcopy
        INCDIR=.
        LIBDIR=$(AVR)/avr/lib
        SHELL=$(AVR)/bin/sh.exe
###### output format can be srec, ihex (avrobj is always created) #######
        FORMAT=ihex
########################## default mcu type #############################
#put the name of the target mcu here (at90s8515, at90s8535, attiny22, atmega603 
etc.)
        MCU=at90s8515
####################### default compiler flags ##########################
        CPFLAGS=-g -O2 -Wall -Wstrict-prototypes -Wa,-ahlms=$(<:.c=.lst)
####################### default assembler flags #########################
        ASFLAGS=-Wa,-gstabs
########################## default linker flags #########################
#       LDFLAGS=-Wl,-Map=$(TRG).map,--cref
        LDFLAGS=-Wl,-Map=$(TRG).map,--cref --defsym __init_mcucr__=0x80

#put the name of the target file here (without extension)
        TRG=test
        
#put your C sourcefiles here 
        SRC= $(TRG).c 

#put additional assembler source file here
        ASRC= 

#additional libraries and object files to link
        LIB=

#additional includes to compile
        INC= 

#early MCU init. weaks
#--defsym __init_mcucr__=0xc0
#--defsym __init_wdtcr__=0x00 
#--defsym __stack=0x7fff

########### you should not need to change the following line #############
#define all project specific object files
        OBJ     = $(ASRC:.s=.o) $(SRC:.c=.o) 
        CPFLAGS += -mmcu=$(MCU)
        ASFLAGS += -mmcu=$(MCU)
        LDFLAGS += -mmcu=$(MCU) 

#this defines the aims of the make process
all:    $(TRG).obj $(TRG).elf $(TRG).rom #$(TRG).eep


#compile: instructions to create assembler and/or object files from C source
%o : %c 
        $(CC) -c $(CPFLAGS) -I$(INCDIR) $< -o $@

%s : %c
        $(CC) -S $(CPFLAGS) -I$(INCDIR) $< -o $@

#assemble: instructions to create object file from assembler files
%o : %s
        $(AS) -c $(ASFLAGS) -I$(INCDIR) $< -o $@

#link: instructions to create elf output file from object files
%elf: $(OBJ)

        $(CC) $(OBJ) $(LIB) $(LDFLAGS) -o $@

#create avrobj file from elf output file
%obj: %elf
        $(BIN) -O avrobj -R .eeprom $< $@

#create bin (ihex, srec) file from elf output file
%rom: %elf
        $(BIN) -O $(FORMAT) -R .eeprom $< $@

%eep: %elf
        $(BIN) -j .eeprom --set-section-flags=.eeprom="alloc,load" 
--change-section-lma .eeprom=0 -O $(FORMAT) $< $@

###### dependecies, add any dependencies you need here ###################
$(TRG).o: $(TRG).c 

#make instruction to delete created files
clean:
        $(RM) $(OBJ)
        $(RM) $(SRC:.c=.s)
        $(RM) $(SRC:.c=.lst)
        $(RM) $(TRG).map
        $(RM) $(TRG).elf
        $(RM) $(TRG).obj
        $(RM) $(TRG).eep
        $(RM) $(TRG).rom
        $(RM) *.bak
        $(RM) *.log


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