Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

Disable Diode in Cyclone III

Hi I have a Cyclone III with Vccio=2.5V and want to connect to a DSP with 3.3V Interface. As I understood AN447 I have to disable the diode in Cyclone III. But how can I do this? I read the Qua...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

Yes, I found a statement in AN447

--- Quote Start ---

Notes to Table 3:

(1) By default, the Quartus II software enables the PCI-clamp diode on any Cyclone III I/O pin assigned as input,

bi-directional, or tri-stated output for 3.3/3.0/2.5-v LVTTL/LVCMOS I/O standard.

--- Quote End ---

So for 2.5V the diode is enabled too...