RE: [Sdcc-user] Preventing SDCC from initializing stack pointer

[<lh...@ua...>]

Felix,

Is there a way for the user application to pass control back to the
bootloader?  I do a similar thing with two pieces of code, but I
intentionally reset the stack pointer at the beginning of the user
application since control cannot pass back to the bootloader.  Would a
similar scheme work for your project?

Lon



-----Original Message-----
From: Felix Brack [mailto:fb...@lt...] 
Sent: Wednesday, April 20, 2005 10:33 AM
To: SDCC
Subject: [Sdcc-user] Preventing SDCC from initializing stack pointer

Hello,

I have an 8051 based hardware running 2 'programs': a firmware and a
user application. The firmware is run from EPROM, the user application
can be downloaded (by the help of the firmware) to a FLASH memory.
When the user application is downloaded, the firmware boot's it.

As my firmware (compiled with SDCC) already initializes the 8051's
stack pointer, I need to tell SDCC not to 'touch' the SP when I build a
user application. The 'problem' is the following code generated by
SDCC:

        .area GSINIT  (CODE)
        .area GSFINAL (CODE)
        .area GSINIT  (CODE)
__sdcc_gsinit_startup:
        mov     sp,#__start__stack - 1
        lcall   __sdcc_external_startup
        mov     a,dpl
        jz      __sdcc_init_data
        ljmp    __sdcc_program_startup

I just need to suppress the instruction loading the stack pointer.
Does anyone know how this is done?

many thanks, Felix




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