Forum Discussion

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

Need "repeater/buffer" for AS config of multiple Cyclone iii slaves

As it states on page 10-14 of the Cyclone III device handbook: "When cascading Cyclone III devices in multi-device configuration, you must connect repeater buffers between the Cyclone III master and ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

The output resistance recommendation is misleading in so far, as you won't most likely find no fast buffer with a that high output impedance. Provide a series termination resistance and adjust it for sufficient low overshoot. You should use the lowest acceptable resistance value to minimize delay. I think, fast single gate LVCMOS buffers are a good option, e.g. LVC1G34, they have an internal output impedance of about 25 ohms.