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Altera_Forum
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16 years ago

False high inputs

Using a Cyclone II 2C20F484C7 fpga, and having some trouble with false high inputs. Basically if I have a switch connected, in other words an open line, it seems to default to reading it as a h...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

An open input without pull-up or pull-down resistor can show any level. Cylone II inputs are high impedance by default. The usual solution is to activate the FPGA internal weak pull-up resistor and apply low level by switching to ground. If you need to switch to a high level, an external pull-down resistor is required.