The VSC837 is a monolithic 68x68 asynchronous crosspoint switch, designed to carry broadband data streams. The non-blocking switch core is programmed through a triple-mode port interface that allows random access programming of each input/output port. A high degree of signal integrity is maintained throughout the chip via fully differential signal paths. The crosspoint function is based on a multiplexer array architecture. Each data output is driven by a 68:1 multiplexer that can be programmed to one and only one of its 68 inputs. The signal path is unregistered and fully asynchronous, so there are no restrictions on the phase, frequency, or signal pattern at each input. Each high-speed output is a fully differential switched current driver with switchable on-die terminations for maximum signal integrity. Data inputs are terminated on die through 100 resistors between true and complement inputs (see Input Termination section for further detail). A triple-mode programming interface is provided that allows programming commands to be sent as serial data or one of two forms of parallel data. The input-referred mode (burst mode) allows an input port to be routed to all outputs in only 4 program cycles. Core programming can be random for each port address, or multiple program assignments can be queued and issued simultaneously. The programming may be initialized to a "straight-through" configuration (A0 to Y0, A1 to Y1, etc.) using the INITB pin. An activity monitor is provided to allow in-system diagnostics. The activity monitor can observe any highspeed input via an internal 69th multiplexer. 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 can be accomplished in hardware, via dedicated power pins for pairs of input and output channels, or in software by programming individual unused outputs with a disable code.