VSC3139

The VSC3139 is a 72x72 asynchronous crosspoint switch, designed to carry broadband data streams. The fully nonblocking switch core is programmed through a multi-mode port interface that allows random access programming of each input/output port. A high degree of signal integrity is maintained throughout the chip by fully differential signal paths.

Each data output can be programmed to connect to one of the 72 inputs. The signal path is unregistered and fully asynchronous, so there are not any restrictions on the phase, frequency, or signal pattern on any input. Each high-speed output is a fully differential switched current driver with ondie terminations for maximum signal integrity. Data inputs are terminated on die through 100Ω resistors between true and complement inputs with a common connection to an internal bias source, facilitating AC-coupling to the switch inputs.

A multi-mode, programming interface is provided that allows commands to be sent as serial data or multiplexed parallel data. Core programming can be sequential on a port by port basis, or multiple program assignments can be queued and issued simultaneously using the CONFIG bit. The INIT feature will reset the entire switch into a "straight-through" configuration (A0 to Y0, A1 to Y1, etc.) or it can be programmed by the user to initialize to any other configuration. Programming of the VSC3139 is via an 11-bit multiplexed ADDR/DATA bus in conjunction with the ALE, RD, WR, CONFIG and INIT pins. Additionally, the CONFIG and INIT signals can be set via an internal control register to reduce the number of signals required to interface with the switch. To lock-in programming of switch connections, INIT, and CONFIG can be disabled through software.

Unused channels may be powered down to allow efficient use of the switch in applications that require only a subset of the channels. Power-down is enabled in software by programming individual unused outputs with a power-down code. A secondary access port allows asynchronous readback and configuration control to take place while the primary programming port is in use.