Sonet/SDH Framer Turns Into Line-Card-On-A-Chip

The Tethys family of Sonet/SDH Multi-Rate Framer ICs collapses the traditional line card into one chip, so it's easier and cheaper than ever to implement next-generation equipment like add/drop multiplexers and digital cross-connect switches. Prior solutions used five or more ICs to implement these functions.

The IC aggregates up to 16 channels of traffic, serializer/deserializer (SERDES), pointer processing, clock and data recovery, and transport overhead (TOH) and path overhead (POH) processing. Manufacturers of line cards for trunk, tributary, and service applications can benefit from the significant savings in power consumption, board design complexity and space, software development, and overall cost.

The line's first two models, the 448 and 4192, fully implement full-duplex Sonet/SDH. The 448 supports 16 channels of OC-3/STM-1, 16 channels of OC-12/STM-4, or 16 channels of OC-48/STM-16, all of which can be mixed in any combination. The 4192 adds support for four channels of OC-192/STM-64. Every port in both models can be independently set for a different data rate, so the equipment can be programmed in the field by simply changing the optical modules.

An on-chip SERDES, clock and data recovery, and clock multiplier unit in the 4192 operate at 2.5 Gbits/s, 622 Mbits/s, and 155 Mbits/s, respectively (see the figure). The chip performs section, line and path overhead processing, framing, scrambling/descrambling, alarm signal insertion/detection, bit-interleaved parity processing, pointer processing, and other functions. Its unique hardware Forced Input Path (FIP) capability enables an entire path to be overwritten directly in alarm conditions, eliminating the need to involve the CPU and switch matrix.

Unlike other framer chips, the 448 and 4192 allow access to both TOH and POH bytes to be extracted from, and re-inserted into, the receive and transmit paths, making all overhead bytes available for additional processing. The 448 has programmable serial ports on the line side, while the 4192 has OIF-compliant line side interfaces SFI-4.1 and SFI-4.2. The interface for both chips is OIF TFI-5.

The 448 and 4192 come in 1400-pin BGA packages. In sample lots, the 448 and 4192 cost $1450 and $1750, respectively. Samples will be available this quarter, with full production later in 2003.