The VSC8111 is an ATM/SONET/SDH compatible transceiver integrating an on-chip clock multiplication unit (PLL) for the high speed clock and 8 bit serial-to-parallel and parallel-to-serial data conversion. The high speed clock generated by the on-chip PLL is selectable for 155.52 or 622.08 MHz operation. The demultiplexer contains SONET/SDH frame detection and recovery. In addition, the device provides both facility and equipment loopback modes and two loop timing modes. The part is packaged in a 100 PQFP with an integrated heat spreader for optimum thermal performance and reduced cost. The VSC8111 provides an integrated solution for ATM physical layers and SONET/SDH systems applications.