link.ld

MEMORY
{
  rom      (rx)  : ORIGIN = 0x00000000, LENGTH = 0x00040000
  ram      (rwx) : ORIGIN = 0x20002000, LENGTH = 0x00004000
}

mtb.c

void mtb_disable(void) {
    MTB_REGS->MTB_MASTER &= ~MTB_MASTER_EN_Msk;
}

void mtb_enable(size_t mtb_size) {
    if ((mtb_size < 16) || (__builtin_popcount(mtb_size) != 1)) {
        // MTB must be at least 16 bytes and be a power of 2
        while (1);
    }

    // scrub MTB SRAM so it's easy to see what has gotten written to
    memset((void *) MTB_REGS->MTB_BASE, 0x00, mtb_size);
    const int mask = __builtin_ctz(mtb_size) - 4;
    
    mtb_disable();
    
    MTB_REGS->MTB_POSITION = 0;
    MTB_REGS->MTB_MASTER = MTB_MASTER_EN(1) | MTB_MASTER_MASK(mask);
}

int main(int argc, char** argv) {
    mtb_enable(4096);
}