The SY87729L is a complete rate independent frequency synthesizer integrated circuit. From a single reference source, this device generates a differential PECL reference frequency for Micrel's SY87721L 10Mbps to 2.7Gbps combined CDR and CMU.The SY87729L generates an exactly correct reference frequency for common data transport protocols. This is especially important in transponder applications, where a standards compliant protocol data unit must be generated downstream, even in the absence of any signal from the associated upstream interface.In addition, SY87729L will generate exactly correct reference frequencies for common data transport protocols augmented by forward error correction codes.For proprietary applications, the SY87729L generates reference frequencies guaranteed to enable the SY87721L CDR to lock to any possible baud rate in its range. SY87729L accepts configuration via a MicroWire™ interface.