The VSC838 is a monolithic 36x36 asynchronous crosspoint switch, designed to carry broadband data streams. The VSC838 also has an internal 37th output channel which is used in conjunction with the Activity Monitor to allow in system diagnostics. 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 36:1 multiplexer that can be programmed to one and only one of its 36 inputs. The signal path is unregistered and fully asynchronous, so there are not any 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 impedance between true and complement inputs (see Input Termination section for further details). A dual mode programming interface is provided that allows programming commands to be sent as serial data or parallel data. 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 INIT pin. 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.