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Altera_Forum's avatar
Altera_Forum
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14 years ago

5V to 3.3V bus and vice versa

MC68000 to CycloneII There is something wrong with quickswich devices. As I know MC68000 cant support 3.3V (some versions can but mine just cant). When i use quickswich any type i only get ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Are the signals going from the Cyclone II to the MC68000 'fast'?

If they are 'slow', then can you consider putting pull-ups to 5V on the signals (bus pull-ups)?

The Cyclone II device can then drive high (to Voh ~ 3.3V), and then tri-state the output driver, the pull-up can then take the signal over the last few volts to 5V.

5V I/O clamps can then be used on the Cyclone II I/O to protect it from the 5V signals (see the DE2 board GPIOs).

Cheers,

Dave