Rainbow Electronics DS3134 - Manual (Page 66)

DS3134
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Bit 15 / Transmit DS0 Channel Enable (TCHEN). This bit must be set for each active DS0 channel in
a channelized application. In a channelized application, although a DS0 channel is deactivated, the
channel can still be set up to route data from the BERT block. In addition, although a DS0 channel is
active, the loopback function (CNLB = 1) overrides this activation and will route receive data to the TD
pin instead of from the HDLC. In an unchannelized mode (TUEN = 1), only the TCHEN bit in T[n]CFG0
needs to be configured.
0 = deactivated DS0 channel
1 = active DS0 channel
5.4 RECEIVE V.54 DETECTOR
Each port within the device contains a V.54 loop pattern detector. V.54 is a pseudorandom pattern that
will be sent for at least 2 seconds followed immediately by an all ones pattern for at least two seconds if
the channel is to be placed into loopback. The exact pattern and sequence is defined in Annex B of ANSI
T1.403-1995.
When a port is configured for unchannelized operation (RUEN = 1), all of the data entering the port via
RD is routed to the V.54 detector. If the Host wishes not to utilize the V.54 detector, then the SLBP
status bits in the Status V.54 (SV54) register should be ignored and their corresponding interrupt mask
bits in ISV54 should be set to 0 to keep from disturbing the Host. Details on the status and interrupt bits
can be found in Section 4.
When the port is configured for channelized operation (RUEN = 0), then it is the Host's responsibility to
determine which DS0 channels should be searched for the V.54 pattern. In channelized applications, it
may be that there will be multiple HDLC channels that the Host wishes to look for the V.54 pattern in. If
this is true, then the Host will perform the routine shown in Table 5.4A. A flowchart of the same routine
is shown in Figure 5.4A