DS3181/DS3182/DS3183/DS3184
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The NR byte is integrated and stored in a register along with a change indication, it is sent to the receive FEAC
controller, and it can be sent to the receive HDLC controller. The byte sent to the receive HDLC controller is
programmable (NR or GC).
The GC byte is integrated and stored in a register along with a change indication, and can be sent to the receive
HDLC controller. The byte sent to the receive HDLC controller is programmable (NR or GC).
10.10.8.10 Receive G.832 Downstream AIS Generation
Downstream G.832 E3 AIS can be automatically generated on an OOF, LOS, or AIS condition or manually
inserted. If automatic downstream AIS is enabled, downstream AIS is inserted when a LOS, OOF, or AIS condition
is declared. Automatic downstream AIS is programmable (on or off). If manual downstream AIS insertion is
enabled, downstream AIS is inserted. Manual downstream AIS insertion is programmable (on or off). Downstream
AIS is removed when all OOF, LOS, and AIS conditions are terminated and manual downstream AIS insertion is
disabled. RPDT will be forced to all ones during downstream AIS.
10.10.9 Clear-Channel Frame Processor
10.10.9.1 Transmit Clear-Channel AIS Generation
Clear-channel AIS generation overwrites the data stream with AIS. If transmit AIS is enabled, the data stream
(payload) is forced to all ones.
10.10.9.2 Receive Clear-Channel Performance Monitoring
Performance monitoring checks the clear-channel signal for alarm conditions. The alarm conditions detected are
LOS and RUA1. A Loss Of Signal (LOS) condition is declared when the B3ZS/HDB3 encoder is active, and it
declares a LOS condition. A LOS condition is terminated when the B3ZS/HDB3 encoder is inactive, or it terminates
a LOS condition.
A Receive Unframed All 1’s (RUA1) condition is declared if in each of 4 consecutive 2047 bit windows, five or less
zeros are detected. A RUA1 condition is terminated if in each of 4 consecutive 2047 bit windows, six or more zeros
are detected.
10.10.9.3 Receive Clear-Channel Downstream AIS Generation
Downstream clear-channel AIS can be automatically generated on a LOS condition or manually inserted. If
automatic downstream AIS is enabled, downstream AIS is inserted when a LOS condition is declared. Automatic
downstream AIS is programmable (on or off). If manual downstream AIS insertion is enabled, downstream AIS is
inserted. Manual downstream AIS insertion is programmable (on or off). Downstream AIS is removed when all LOS
conditions are terminated and manual downstream AIS insertion is disabled. All bits will be forced to ones during
downstream AIS.
10.11 HDLC Overhead Controller
10.11.1 General Description
The DS318x devices contain built-in HDLC controllers (one per port) with 256-byte FIFOs for insertion/extraction of
DS3 PMDL, G.751 Sn bit and G.832 NR/GC bytes and PLCP NR/GC bytes.
The HDLC Overhead Controller demaps HDLC overhead packets from the DS3/E3 data stream in the receive
direction and maps HDLC packets into the DS3/E3 data stream in the transmit direction.
The receive direction performs packet processing and stores the packet data in the FIFO. It removes packet data
from the FIFO and outputs the packet data to the microprocessor via the register interface.
The transmit direction inputs the packet data from the microprocessor via the register interface and stores the
packet data in the FIFO. It removes the packet data from the FIFO and performs packet processing.
The bits in a byte are received MSB first, LSB last. When they are output serially, they are output MSB first, LSB
last. The bits in a byte in an incoming signal are numbered in the order they are received, 1 (MSB) to 8 (LSB).
However, when a byte is stored in a register, the MSB is stored in the lowest numbered bit (0), and the LSB is
stored in the highest numbered bit (7). This is to differentiate between a byte in a register and the corresponding
byte in a signal.