Purpose of the RESET#/OE# circuit controlled by Q1 on the FX2 Mass Storage Reference Design.

Question: What is the purpose of the RESET#/OE# circuit controlled by Q1 on the FX2 mass storage reference design?

 

Answer:

The CY4611 v2.30 design interfaces to the CF in memory mode. The CF will power up in memory mode if it is hot-plugged into the CF socket. If the board is powered up with the CF installed, OE# must be high when the CF comes out of power-on reset. If OE# is low, the CF will come up in IDE mode.Since the CF power is tied to VBUS, CF power will come up more quickly than power to the FX2. The FX2 cannot pull OE# up before it has power. To provide a pullup to OE# while the FX2 is coming out of reset, Q1 is configured to pull OE# high (to VBUS) while the CF is powering up. After the FX2 reset period ends, FX2 is able to control OE#.