Functional Description

TRANSMITTER

The transmitter part consists of the multi frame overhead handler and the frame builder itself.

Multi Frame Overhead Handler

This block is responsible for providing the overhead bits according to the current frame type. These bits are then forwarded to the frame builder unit that inserts them

into the outgoing data stream.

Frame Builder

The frame builder performs all the tasks necessary to output a valid frame that complies with the E1 carrier system.

Basic Frame Synchronizer Generator

This block synchronizes the incoming data and provides a basic frame reference signal that identifies every bit within a basic frame.

Multi Frame Generator

The multi frame generator builds a multi frame reference signal based on the basic frame reference and provides the associated interrupts.

TS0 Bit Insertion

This unit automatically inserts all the special bits on the fly into time slot 0. It uses the frame reference signal to insert the corresponding bits. It inserts the basic frame

alignment, the CRC4 multi frame alignment signal, the computed CRC4 value plus the configured special bits.

CRC4 Calculation

This block computes the CRC4 value on the outgoing data stream and feeds it back to the TS0 bit insertion block.

RECEIVER

The receiver part comprises the synchronizer block and the analyzer block.

Snychronizer

The synchronizer samples the incoming data frame and generates the corresponding frame reference signal and the necessary interrupts.

Basic Frame Aligner

This block synchronizes the incoming data and provides a basic frame reference signal that identifies every bit within a basic frame.

Multi Frame Aligner

The multi frame aligner detects multi frame structures and builds a multi frame reference signal based on the basic frame reference and provides the associated

interrupts.

CRC4 Checker

This unit computes the CRC4 on the incoming frame and compares it with the received CRC bits and provides the corresponding status signals.

Analyzer

This unit uses the frame reference signal to analyze the incoming frame.

Alarm Detector

This unit samples the alarm bits of the incoming frame. It registers them and outputs an alarm history. Plus it marks the reception of the alarm indication signal.

Monitor Counter

The monitor counter holds error counters that keep track on the CRC4, FAS and E-bit errors that have been detected on the incoming frames.

TS0 Signal Capture

This block samples the bits in time slot 0 and stores them into a register bank for further processing. The register bank can hold the TS0 bits of 8 consecutive frames

within a multi frame structure.

AISLOS Detector

This unit detects the alarm indication signal (AIS) and the 2Mbit loss condition.