The VSC8140 is a SONET/SDH compatible transceiver with integrated clock generator for use in SONET/ SDH systems operating at a 2.48832Gb/s data rate. The internal clock generator uses a Phase-Locked Loop (PLL) to multiply either a 77.76MHz or 155.52MHz reference clock in order to provide the 2.48832GHz clock for internal logic and output retiming. The 16-bit parallel interface incorporates an on-board FIFO eliminating loop timing design issues by providing a flexible parallel timing architecture. In addition, the device provides both facility and equipment loopback modes and two loop timing modes. The VSC8140 operates using a 3.3V power supply, and is available in either a thermally-enhanced 128-PQFP or a thermally-enhanced 208-pin TBGA package.