FAQ: Digital Crosspoint Switch Frequently Asked Questions

Document created by daverowe Employee on Aug 30, 2013Last modified by daverowe Employee on Mar 20, 2014
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This page contains frequently asked questions about Analog Devices X-stream family of digital crosspoint switches.  This page is intended to contain questions and answers that are applicable to the entire family.  Specific product questions can be submitted to the Engineer Zone Switches and Multiplexers forum or other relevant application specific forums.  Use this link to search for digital crosspoint switch questions in the Analog Devices Engineer Zone.

 

Q. What data rates or range of data rates are supported?

A. The digital crosspoint switch products are asynchronous and protocol agnostic and therefore support any data rate independently per lane up to the maximum rated data rate listed in the product datasheet

 

Q. What serial data protocols are supported?

A. The digital crosspoint switch products are asynchronous and protocol agnostic and therefore can support almost any physical layer protocol assuming the data is binary formatted (NRZ or RZ) and data rate is within the maximum operating data rate listed in the datasheet. 

 

Q. When should I use ac-coupling vs. dc-coupling on the high-speed serial lanes?

A. Ac-coupling isolates the dc current between a transmitting Tx device and a receiving Rx device. This is useful for dc level translation, hot-swap protection and to prevent dc current flowing between different supply domains such as in card-to-card or chassis-to-chassis connections.  Ac-coupling has the disadvantage of a setting a low frequency cutoff thereby requiring that the serial data be scrambled or encoded such that it has a equal number of zeroes and ones on average and a contrained number of consecutive identical digits (CIDs). 

 

Q. Can I connect one input to multiple outputs?

A. Yes, the digital crosspoint switch products are non-blocking which means that any output can receive data from any input regardless of the connection states of other outputs. 

 

Q. Does changing the crosspoint connectivity affect the state of previously configured connections?

A. No.  Each output can receive data from any input regardless of the connection states of other outputs.  If the connectivity of a specific outputs changes, other outputs' connection states will remain unchanged.

 

Q. What should I do with unused inputs or outputs?

A. In general, the high-speed serial inputs and outputs have integrated termination resistors to termination supply voltages.  If any of these pins are unused, they can be left floating.  Unused input control pins should be pulled up or down as recommended in the corresponding product datasheet.  Unused output control pins such as interrupts can be left floating unless otherwise required in the product datasheet. 

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