DM642 use flash to start the timing problem.

I use 8 bit flash as DM642 start-up mode, I observed CE1 sequence, after reseting there is 1ms low level, then also there are Dozens of  milliseconds level change to complete 1K read, but when I take the flash off,(not connected to the flash), CE1 only  has 1ms low level, then a straight to maintain high, no longer read.So I would like to ask that is  this  a normal phenomenon? DM642 can automatically detect whether  is there  a  flash?