Hi, I have built a boot loader which chooses the recent between 2 versions of the program burnt on the flash. The only problem is that I need 2 copies of the interrupt and reset vectors...one for each image...
I have succeeded locating the 2 copies in different locations as I wish but I'm having trouble with the CSEG AT statement which needs to be changed in the STARTUP.A51 of the boot loader. I want to do this during runtime so that when the boot loader decides which image it needs to run it will tell the hardware where the interrupt vectors are located using th CSEG.
Is this technically possible? and if the answer is yes...how is it done? I didnt really understand good enough the CSEG statement.
Thank you very much.
with the CSEG AT statement which needs to be changed during runtime if that was possible the compiler/linker would need to have the ability to dynamically at run time relocate code in read only memory.
to get you started this in the part residing off loc sero
CSEG AT 000h ;reset ljmp startup CSEG AT 003h ;int 0 ljmp ISC_EI0 ... ... ... startup:; setb GBboot mov dptr,#0fbffh mov a,#0 movc a,@a+dptr jnz startAP ; if last page of flash is erased we are in app mode ljmp ?C_STARTUP startAP: clr GBboot ljmp APPBASE + 060h
this in each of the two
..... CSEG AT APPBASE + 060h ;int 20 ljmp ?C_STARTUP
Erik