Re: VIO pin connection

["Eric de Jong" <info@simultime.nl>]

In a 5V signaling environment of PCI 33 (which is in most of the PC's) you
may tie the VIO of the asic directly to the 5V, as the VIO of the PCI
connector is also 5V.

you mentioned earlier "by a resistor". don't. and do not forget to decouple
the VIO of the asic.

In a 3.3V signaling environment, this is not PCI compliant, as the clamping
diodes are then at 5V. If you use the asic in a 3.3V signaling environment,
you should connect the VIO pins to VIO of the PCI connector or directly to
the 3.3V.




>
>  Let me restate my original question.
>
>   Is it Ok to connect VIO pins of a 3.3v ASIC
>   that has 5v input tolerant PCI pads (the ASIC
>   supports 3.3v signaling and uses 5v for input
>   clamping) to connect to +5v supply directly
>   instead of VIO pins of a PCI connector.
>
>   In 3.3v environment, the VIO is 3.3v and inputs
>   are clamped to 3.3v. In 5v environment, the VIO
>   is at 5v and the inputs are clamped to 5v.
>
>   Are there any issues if we always clamp inputs
>   to 5v by connecting VIO of an ASIC to 5v rail
>   instead of VIO.
>