regards,
Ramzi Ammar
Texas Instruments
At 05:23 PM 4/16/98 -0400, O'Donnell, John wrote:
>SI Practitioners,
>
>What is the state of the art in commercially available VMEbus
>transceivers (i.e '16245-type bus transceiver in surface mount 48-pin
>TSSOP packages)?
>
>I have a VME-hosted 6U board that provides a bridge between the VMEbus
>and a side bus implemented on the VMEbus J2 Connector rows A and C
>using Futurebus technology (i.e BTL transceivers). Activity on the two
>buses is asynchronous with respect to the other bus, meaning that the
>VME bus transceivers can turn on to drive a master transaction to the
>VMEbus at any time during receipt of a slave transaction on the side
>bus. The ground lift, or ground bounce produced when the VMEbus drivers
>turn on is sufficient to cause data glitches on the local bus outputs of
>the side bus BTL transceivers. When the VMEbus driver turn-on happens
>to coincide with the sampling edge of the side bus data strobe used to
>capture side bus slave data the amplitude and width of the data glitch
>is sometimes enough to be captured in the side bus slave data latches.
>
>The board design was based on a heritage design which used 74FCT16245
>bus transceivers to interface to the VMEbus. These devices produced
>humongous ground bounce effects and serious data error problems on the
>side bus. These have since been changed to 74ABT16245. This change has
>produced a marked improvement in the side bus data integrity but there
>are still occasional errors traceable to ground bounce effects when the
>'ABT drivers turn on. Is there a better technology available for driving
>a 21-slot VMEbus backplane with standard resistive terminations such
>that the driver di/dt is restrained enough to result in a tolerable
>ground bounce effect?
>
>Regards,
>John O'Donnell
>AYDIN Telemetry
>
>