The DOHP155T is a monolithic integrated circuit that processes the section overhead of STM-1 streams at up to 155.52 Mb/s and implements payload alignment and path termination for VC-4 payload.
    The DOHP155T receives dual SDH STM-1 frames via a bit serial interface and it processes dual regenerator section overhead and APS bytes (K1, K2). It support 1+1 MSP protection. Only the “multiplexer section” overhead on the selected STM-1 data stream is processed. On the outgoing STM-1 stream, the STM-1 data excluded REG Overhead, K1/K2 and B2 are duplicated. It performs framing (A1, A2), de-scrambling, detects alarm conditions, and monitors regenerator section and multiplex section bit interleaved parity (B1, B2), accumulating error counts at each level for performance monitoring purposes. Multiplex section far end block error (REI) indications (M1) are also monitored. A 1, 16 bytes section trace (J0) sequence may be processed.
    The DOHP155T transmits SDH STM-1 frames, via a bit-serial interface, and formats regenerator section and multiplex section overhead appropriately. It performs framing pattern insertion (A1, A2), scrambling, alarm signal insertion, and creates regenerator section and multiplex section bit interleaved parity (B1, B2) as required to allow performance monitoring at the far end.
    Multiplex section far end block error (REI) indications (M1) are also inserted. A 1, 16 bytes section trace (J0) sequence may be inserted.
    The DOHP155T generates the transmit payload pointers (H1, H2) and inserts the synchronous payload envelope (virtual container) from an ADD bus or data interface in the transmission stream. Frequency offsets and phase differences between the transmission data stream and the ADD bus are accommodated by pointer adjustments in the transmission stream.
    The DOHP155T can be programmed to pass part or all of the path overhead byte on the ADD bus through unaltered.
    The transmitter and receiver are independently configurable to allow for different reference timing interfaces. The DOHP155T is configured, controlled and monitored via a generic 8-bit microprocessor bus interface.