ODU0 Framer/Overhead Processing with GMP

General Description

The Xelic Optical Transport Network (OTN) Framer Core (XCO0) performs GMP mapping/demapping, Optical Channel Data Unit (ODU) and Optical Channel Payload Unit (OPU) overhead/data processing, aligns incoming ODU frames, and provides overhead interpretation with error detection and performance monitoring. The XCO0 contains independent transmit and receive processors with external ports for overhead insertion and extraction. System side signals are transferred at a nominal rate of 1.24Gb/s using an 8-bit data bus operating at 154.87MHz or an ODU0 rate (streaming mode) using an 8-bit data bus operating at 155.52Mb/s. Line side data is transferred at an ODU0 rate using an 8-bit data bus operating at 155.52MHz.

The XCO0 Transmit Processor accepts payload signals or ODU0 streaming data for transport. Incoming data is GMP mapped into the OPU0 payload cavity of generated ODU0 frames as outlined in G.709 specification section 17.7.1. In both GMP mapping or streaming modes of operation, the transmit processor inserts ODU0/OPU0 overhead, calculates and inserts parity, automatically generates Backward Defect Indication (BDI) signaling, and scrambles generated frames. Support is provided for up to 6 levels of tandem connection overhead insertion. Programmable Trail Trace Identifier buffers are implemented for Section Monitoring (SM), Path Monitoring (PM), and Tandem Connection Monitoring overhead insertion. Diagnostics support includes optional corruption of inserted parity, corruption of scrambling, frame alignment signal corruption, and maintenance signal insertion. Programmable fixed byte and PRBS payload mapping types are supported.

The XCO0 Receive Processor contains a configurable frame alignment unit with programmable options for OOF/OOM and LOF/LOM algorithm state transitions. Incoming ODU frames are de-scrambled (optional) and aligned for OTN overhead processing. ODU and OPU overhead information is extracted to both internal register locations and an external overhead port. Frame alignment signal overhead is interpreted to detect and report various conditions which include OOF, LOF, LOA, OOM, LOM, and LOMA. ODU AIS, ODU LCK, ODU OCI and client generic AIS maintenance signals are detected with optional interrupt generation. OPU payload type mismatch error conditions are detected and support is provided for programmable payload type accept and inconsistent thresholds. Incoming payload data is interpreted and GMP demapped before being made available on the system side interface.

OTN Performance counters (configurable for error sync mode) are provided for the accumulation of inserted (XCO0 transmit processor) and detected (XCO0 receive processor) positive and negative justification (1x and 2x) events along with BIP-8 parity and BEI errors for OTU SM, ODU TCMi, and ODU PM (XCO0 receive processor). All counters are configurable for saturating latch and clear operation or periodic error sync auto-update mode.

The XCO0 provides facility and terminal loopback modes of operation using Transmit and Receive Processor data path configurations for system debug purposes.

A 16-bit generic register interface for access and configuration of internal memory mapped locations is included.


  • Suitable for FPGA and/or ASIC implementations.
  • Integration support and maintenance available.
  • XCO0 core available under flexible single use licensing terms with netlist or source code deliverables.
  • Provides for streaming and normal modes of operation.
  • Implements 16-bit register interface for programming of internal registers.
  • Complies with ITU-T G.709 and ITU-T G.798 specifications.
  • Supports transmit and receive facility and terminal loopback configurations.
  • Accepts streaming ODU0 frames or payload signals for GMP mapping.
  • Performs GMP demapping and payload interpretation.
  • Flexible insertion and extraction of ODU, and OPU overhead byte information.
  • Inserts OTU SM, GCC0, and RES overhead through internal register control or an external overhead port.
  • Inserts ODU RES, TCM ACT, FTFL, PM, EXP, GCC1, GCC2, and APS/PCC overhead through internal register control or an external overhead port.
  • Provides 6 levels of tandem connection overhead insertion.
  • Programmable positive (1x/2x) and negative justification (1x/2x) counters provided for asynchronous 1000 BASE-X payload types with user defined interval or errored second accumulation.
  • Optionally inserts ODU AIS, ODU LCK, ODU OCI and client generic AIS maintenance signals.
  • Provides optional descrambling with polynomial corruption capability for diagnostics.
  • Performs ODU0 frame alignment with programmable OOF/OOM and LOF/LOM detection.
  • Interprets and extracts OTU SM, GCC0 and RES overhead information to internal register locations with programmable accept and inconsistent maskable interrupt capability.


  • Traffic Manager
  • OTN/SONET add/drop multiplexers
  • Digital cross connects
  • OTN and/or SONET/SDH line cards
  • Test equipment