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To command signal FX2_PS_EN, read the reference firmware code.
IOD = 0x03; // Enable PS_ON and disable PROG_B
OED = 0x03; // Configure PS_ON and PROG as outputs

When slide switch S2 is in the left position ( = FX2 PON : power rails conditionally on depending on signal FX2_PS_EN), signal PS_EN is set to signal FX2_PS_EN driven by the EZ-USB FX2LP USB FX2 microcontroller under user control.

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Figure 35: S2 on position FX2 PON (PS_EN = FX2_PS_EN = x ).

1. Dynamic full power operation (PS_EN = high): when the EZ-USB FX2LP USB FX2 microcontroller sets signal PS_EN = FX2_PS_EN = high, power rails 2.5V and 1.2V are enabled.
   This setting can be useful for .
2. Dynamic low power operation (PS_EN = low): when the EZ-USB FX2LP USB FX2 microcontroller resets signal PS_EN = FX2_PS_EN = low, the following components are switched off:

• FPGA core logic (1.2V)
• DDR SDRAM (2.5V)
• FPGA bank 3 (2.5V)
• VREF (2.5V)
• VCCCIO0 (2.5V) FPGA bank 0