The EZ-USB Technical Reference Manual of the AN2131 and friends shows that all external memory read and write strobe signals are active (low) for two CLK24 cycles (see Fig. 13-1 to 13-4). Important: That this is only true if the wait states are disabled as described in Sec. B.2.2.
After reset the default is one wait state which extends the strobe signals to four CLK24 cycles.
Bits 0 to 2 of the SFR CKCON have to be set to 0 explicitly for zero wait states with a strobe width of two.