the cortex_m4 technical reference manual say that:from 0x00000000 to 0x20000000 is code map,from 0x20000000 to
0x40000000 is sram,

but the k64 technical reference manual say that:the sram map is from 0x1fff0000
why the inital address of sram is in the code map of cortex_m4?