
XRT86SH221
PRELIMINARY
39
SDH-TO-PDH FRAMER/MAPPER WITH INTEGRATED 21-CHANNEL E1 SH LIU
REV. P1.0.5
4.2
FUNCTIONAL BLOCKS
The Voyager-Lite device is functionally, as well as architecturally, divided into the following blocks and
modules:
I
Transceiver Interface
I
STM-0/1 Transmit Framer (Tx Transport Overhead Processor)
I
STM-0/1 Transmit TOH (Transport OverHead) Interface
I
STM-0/1 Receive Framer (Rx Transport Overhead Processor)
I
STM-0/1 Receive Overhead Interface
I
STM-0/1 Transmit Pointer Processor (Tx Path Overhead processor)
I
STM-0/1 Transmit POH (Path OverHead) Interface
I
STM-0/1 Receive Pointer Processor (Rx Path Overhead Processor)
I
STM-0/1 Receive POH (Path Overhead) Interface
I
VT Mapper
I
21 Port Cross Connect
I
E1 Receive Framing Synchronizer
I
LIU Control Interface
I
LIU Modules
I
Microprocessor Interface
I
Interrupt Controller
I
Performance Monitor
The operations and functions of these blocks are discussed in detail in the following sections. This section
gives an overview of the operation of this device.
4.3
SDH TRANSMIT DATA FLOW
The SDH transmit blocks allow flexible insertion of transport and path overhead bytes through both hardware
and software. The blocks also perform primitive SDH tasks such as data scrambling, BIP-8 calculation and
insertion, and fixed stuff columns insertion. The blocks are used to transmit an SDH STM-1 stream with any
legal concatenation composition. The location of the SPE within the STM-1 frame is fixed with a pointer offset
of 522, which results in the J1 byte immediately trailing the last Z0 byte in the transport overhead.
Figure 13
shows the general structure of an SDH transmitter. As in the case of SDH receive blocks, the SDH
transmit blocks are reusable blocks that are configured to transmit any compositions of any STM-N stream (3c
and 1). The SDH transmit block consists of a transport section (txspoh_proc and txspoh_cont blocks) and 5
path sections.
The txspoh_cont path overhead block receives path overhead data from both software and hardware and
allows software to select the version that is forwarded to the txspoh_proc path processor block. Software can
also specify actions on the SPE data such as AIS-P insertion and RDI-P insertion.
The txspoh_proc block receives payload data from the VT Mapper interface and path overhead data from the
txspoh_cont block and performs a multiplexing function using the location information from the txspoh_proc
transport processor block. The txspoh_proc block also generates the H1/H2 pointer bytes and provides them
on its output data port at the appropriate instances in the transport overhead. Since there can be multiple path
blocks for a SDH transmitter, the txspoh_proc block only puts bytes onto its output data ports when the current
transmit time slot belongs to its path. Otherwise, zeros are placed on the output data port. The data from all the
txspoh_proc blocks are ORed together before being forwarded to the txstoh_proc block.
The txstoh_cont transport control block receives transport overhead data from both software and hardware and
allows software to specify the version that is forwarded to the txstoh_proc block. Software also specifies
actions such as AIS-L insertion, LOS insertion, and BIP-8 error insertions.