Low-order channel adaptation function block LPA and asynchronous physical interface module PPI

After the E1 electrical signal enters the PPI, it undergoes clock extraction and data regeneration and is sent to the mapping and demapping processor with jitter suppression.

The PDH interface module detects and terminates the T_ALOS alarm. When a T_ALOS alarm is detected, a full "1" signal is inserted into the higher level circuit.

The LPA completes the data adaptation function.

If T_ALOS alarm is detected, UP_E1_AIS alarm is reported, but T_ALOS can suppress UP_E1_AIS by setting alarm correlation rules.

If the uplink data rate deviation is too large, it will cause the FIFO (First In First Out) of the transmit side of the low-order channel to overflow and report the LP_T_FIFO alarm.

High-order channel adaptation function block (HPA) and low-order channel termination function block (LPT)

The function of LPT is to insert POH (Path Overhead) in C-12 to synthesize VC-12.

The LPT inserts the "signal marker" into bits b5-b7 of the V5 byte, calculates the BIP-2 for the previous multi-frame data, and places the result in bits b1 and b2 of the V5 byte of the current frame. If a "channel terminal error" is detected in the downlink data during the downlink signal processing flow, bit b3 of V5 byte will be set to "1" in the next frame, generating the return alarm LP_REI.

The HPA adapts the VC-12 to a TU-12 and maps it to a higher-order VC-4 for delivery to the cross-over board. the frame offset in bytes between the VC-12 and the VC-4 is indicated by a TU-12 pointer. Each frame determines a V (one of V1, V2, V3, V4) byte, and every 4 frames form a complex frame. the H4 byte used to determine the value of the V byte is also generated in this function block.