TMS320F28027F: Clear all ram contents but keep auto initialization variable

Hi Jack,

standard C startup routine should clear all static storage variables (SSV) and initialize those which have initializer. As I understand it, since RAM with ECC on these MCUs is unusable without initial initialization (see DxINIT, LSxINIT etc registers), boot ROM clears (initializes) all RAM, so that C compiler kind of doesn't have to clear SSV. This is true but only for normal power on boot. While debugging, RAM clear routine in boot ROM isn't called and SSV are not cleared. Linkers RAM initialization model doesn't help, since often it's necessary to restart program without reloading.

In TI C compiler for C2000, you may define  _system_pre_init() routine, which is called prior to initialization of variables with initializer. You may add there code to somehow clear .ebss section.

1. You may for example dedicate some memories like GS0 for .ebss, then use GS0INIT register to initialize GS0.

2. You may also use memset() to initialize .ebss.

in cmd file:

.ebss : > RAMGS23, PAGE = 1, RUN_START(_EbssStart), RUN_SIZE(_EbssSize), table(ebsstable)

To use linker ??_START and ??_END addresses, .ebss has to be contiguous. This is why I concatenated GS2 and GS3 memories.

in code

#if defined(_DEBUG)
#include <string.h>

int _system_pre_init(void)
{
    extern int EbssSize, EbssStart;

    memset(&EbssStart, 0, (size_t)&EbssSize);

    return 1;
}
#endif

Edward