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On-board 4xDIP switch S1 used for system and user settings.
System setting
Slide Switch S1A
Switch S1A is used to connect the USB controller to the IIC serial EEPROM:
- when switch S1A is "ON", serial IIC EEPROM is connected to the USB controller,
- when switch S1A is "OFF", the USB FX2 microcontroller is disconnected from the EEPROM.
Turn S1A on when programming the USB EEPROM (storing the USB vendor ID and device ID).
TE USB FX2 module is powered on when S1A is turned off: this will force the USB controller to provide its default (Cypress) vendor ID and device ID.
Slide Switch S1B
Switch S1B is used to control DC-DC converters:
- when switch is "OFF", converters are controlled by the USB controller;
- when switch is "ON", converters are enabled regardless of USB controller actions. At start-up, the USB controller switches off 1.2V, 1.5V and 2.5V power rails and starts up the module in low-power mode. After enumeration, the USB controller firmware switches the 1.2V, 1.5V and 2.5V power rails on, if enough current is available from the USB bus.
User Settings
Switches S1C and S1D can be used as user switches. Switches are active-low. Pull-up resistors should be defined in user constrains file (UCF) to use this switches in FPGA design. See the table below for details