I erase flash memory L051 with uart,fail ,return back 1F,but 44 BB is ok,return 79,what's wrong?

[Lxian.12]

command orders:

7F return 79

92 6D return 79

7F return 79

44 BB return 79

FF FF 00 or FF FE 01 OR FF FD 02 return 1F