Sigma DE2-70 User Manual

 

DE2-70 User Manual

 

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position and then reset the board by turning the power switch off and back on; this action 

causes the new configuration data in the EPCS16 device to be loaded into the FPGA chip. 

 

 

 

Figure 5.2.    The AS configuration scheme. 

 

In addition to its use for JTAG and AS programming, the USB Blaster port on the DE2-70 board 

can also be used to control some of the board's features remotely from a host computer. Details that 

describe this method of using the USB Blaster port are given in Chapter 3. 

 

The DE2-70 board provides four pushbutton switches. Each of these switches is debounced using a 

Schmitt Trigger circuit, as indicated in Figure 5.3. The four outputs called KEY0, KEY1, KEY2, and 

KEY3 of the Schmitt Trigger devices are connected directly to the Cyclone II FPGA. Each switch 

provides a high logic level (3.3 volts) when it is not pressed, and provides a low logic level (0 volts) 

when depressed. Since the pushbutton switches are debounced, they are appropriate for use as clock 

or reset inputs in a circuit. 

 

 

Figure 5.3.    Switch debouncing.