The TQ8213 operates in two different time-division multiplexing modes, making it extremely flexible for use in telecom and datacom applications. The serial 2.48832 Gb/s data stream can be generated from either a 16-bit wide 155.52 MHz data stream or a 32-bit wide 77.76 MHz data stream. Data integrity may be ensured through a byte-wise parity check, which occurs in parallel with the incoming data stream. An external parity alarm is set whenever a parity check error is detected. Transmit clocking is selectable from either an internal or external Voltage Controlled Oscillator(VCO) as well as a selectable external or internal Phase Locked Loop (PLL). The selected clock source may be monitored at HCKOUT. The internal PLL utilizes an external reference clock, REFCLK, to aid in timing generation. The reference clock may be one of seven commonly used system frequencies. A TTL level LOCK signal is supplied to indicate when the phase difference between the external reference clock and the internal divided down clock is less than /4 radians. Operating from a single +5V supply, the TQ8213 will provide fully compliant functionality and performance. Direct-connected TTL levels are used with both of the input modes. The TQ8213 is fully compliant with SONET/SDH jitter specifications.