请问5509A存储器映射为什么会出现“memory map prevented read of target memory at 0x00000050@DATA”？

在ccs3.3的Watch Window查看中断控制寄存器IER0时出现以下问题：
*IER0  在 memory map prevented read of target memory at 0x00000050@DATA
寄存器在头文件定义方法：
#define IER0         (volatile unsigned int *)0x0000 //中断使能寄存器0

请问为什出现了“memory map prevented read of target memory at 0x00000050@DATA”现象？？

我的CMD文件：
/*-map -u _Reset*/
-m DMD730_DSPV11.map
-c
-u _Reset
-stack 2048
-sysstack 2048
MEMORY [
MMR: origin = 0x00000, len = 0x00100
VECT: origin = 0x00200, len = 0x00100
VECT1: origin = 0x00300, len = 0x00100
DRAML32K1: origin = 0x00400, len = 0x00800
DRAML32K2: origin = 0x00C00, len = 0x00800
DRAML32K3: origin = 0x01400, len = 0x06C00
DRAMH32K: origin = 0x08000, len = 0x07fff
PROG0: origin = 0x10000, len = 0x0ffff
SARAM: origin = 0x20000, len = 0x20000
]
SECTIONS
[
.vectors:[]>VECT
vectors:[]>VECT1
.stack:[]>DRAML32K1
.sysstack:[]>DRAML32K2
.sysmem:[]>DRAML32K3
.cio:[]>DRAML32K3
.bss:[]>DRAMH32K
.data:[]>DRAMH32K
.cinit:[]>DRAMH32K
.const:[]>DRAMH32K
.text:[]>PROG0
.switch:[]>SARAM
]