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hi, i want to debug program in external ram, it is my set, but it doesn't work. keil platform. the external ram using bank1 ne3.
1. Optioin target ROM1 checked, start 0x68000000, size 0x80000, select startup RAM1 checked, start 0x68080000, size 0x20000
2. flash download RAM for algorithm start 0x68080000, size 0x2000
programming algorithm start 0x68000000, size 0x00080000
debug initialize file
FUNC void Setup (void) { SP = _RDWORD(0x68000000); // Setup Stack Pointer PC = _RDWORD(0x68000004); // Setup Program Counter _WDWORD(0xE000ED08, 0x68000000); // Setup Vector Table Offset Register _WDWORD(0x40021014, 0x00000100); // RCC->AHBENR FSMC Enable _WDWORD(0x40021018, 0x000001E0); // RCC->APB2ENR GPIOD GPIOE GPIOF GPIOG _WDWORD(0x40011400, 0xFFBBFFBB); // GPIOD CRL _WDWORD(0x40011404, 0xBBBBBBBB); // GPIOD CRH _WDWORD(0x40011800, 0xBFFFFFBB); // GPIOE CRL _WDWORD(0x40011804, 0xBBBBBBBB); // GPIOE CRH _WDWORD(0x40011C00, 0xFFBBBBBB); // GPIOF CRL _WDWORD(0x40011C04, 0xBBBBFFFF); // GPIOF CRH _WDWORD(0x40012000, 0xFFBBBBBB); // GPIOG CRL _WDWORD(0x40012004, 0xFFFFFBFF); // GPIOG CRH _WDWORD(0xA0000010, 0x00001011); // FSMC BCR3 _WDWORD(0xA0000014, 0x00000300); // FSMC BTR3 _WDWORD(0xA0000114, 0x0FFFFFFF); // FSMC BWTR3 }
SCB->VTOR = ((uint32_t)0x68000000);
Yes, I guess it take some effort to correctly configure the CPU and clocks, set up the GPIO and FSMC, but I'd hardly say the ordering or requirements are "unknown". You've basically got to do the same things as your current startup code is going to have to do.
It's clearly easier to use internal RAM for such things.
There may be needs to configure some clocking too - if the external memory is DRAM and there isn't a refresh clock then the downloaded program can be garbled even before the debugger sets the PC and starts to run the program.
As noted - same requirements as there is for normal startup sequence to put the machine in a state where this external RAM is fully usable.