rv1126执行io命令修改寄存器无效

[root@RV1126_RV1109:/]# io
Raw memory i/o utility - $Revision: 1.5 $

io -v -1|2|4 -r|w [-l ] [-f ] []

-v         Verbose, asks for confirmation
-1|2|4     Sets memory access size in bytes (default byte)
-l <len>   Length in bytes of area to access (defaults to
           one access, or whole file length)
-r|w       Read from or Write to memory (default read)
-f <file>  File to write on memory read, or
           to read on memory write
<addr>     The memory address to access
<val>      The value to write (implies -w)

Examples:
io 0x1000 Reads one byte from 0x1000
io 0x1000 0x12 Writes 0x12 to location 0x1000
io -2 -l 8 0x1000 Reads 8 words from 0x1000
io -r -f dmp -l 100 200 Reads 100 bytes from addr 200 to file
io -w -f img 0x10000 Writes the whole of file to memory

Note access size (-1|2|4) does not apply to file based accesses.

[root@RV1126_RV1109:/]# io -4 -r -l 4 0xfe010050
fe010050: 00001177
[root@RV1126_RV1109:/]#
[root@RV1126_RV1109:/]# io -4 -w -l 4 0xfe010050 0x333333
[root@RV1126_RV1109:/]#
[root@RV1126_RV1109:/]# io -4 -r -l 4 0xfe010050
fe010050: 00001177

通过io命令修改寄存器无效，有人知道怎么回事吗？