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COMSPHERE 3600 Series Data Service Units
4-8 March 1999 3610-A2-GB41-60
TDM Applications
The TDM capability can be used in a variety of
configurations to enhance DDS service. Configurations
discussed here include point-to-point multiplexing, a
TDM backbone circuit with extensions, diagnostic
extension, digital sharing, multiplexing and digital
sharing, and FEP port-sharing.
Single-Port Async/Sync Support
When operating with the Async→Sync configuration
option enabled, a single-port point-to-point or multipoint
circuit can operate using nondisruptive diagnostics
(Diag Type: NonD).
Point-to-Point Single-Port Async/Sync Capability
When operating with the Async→Sync configuration
option enabled, a single-port point-to-point circuit can
operate using nondisruptive diagnostics. The control
DSU’s port speed and the tributary DTE port speeds must
be set to the same rate (see Figure 4-4). Note that the
tributary DSUs are configured as a single port-sharing
group (Share DevA: Enab).
Refer to Table 1-2 of the COMSPHERE 3600 Series
Data Service Units, Model 3610 and 3611, Operator’s
Guide for the maximum diagnostic rate that can be run for
various asynchronous-to-synchronous configurations.
Note that in this table, None indicates that no excess
bandwidth is available for nondisruptive diagnostics.
When the DSU is configured for nondisruptive
diagnostics and the Async→Sync configuration option is
enabled, the DTE rate cannot operate underspeed for
diagnostics since the DTE is now operating in
synchronous mode. In addition, the maximum diagnostic
rate available is 1600 bps, but the DSU’s firmware
overrides any selected rate with a speed up to 2400 bps if
more bandwidth is required for diagnostics.
Asynchronous port speeds of 150, 300, 600, and
1800 bps may be obtained by oversampling; oversampling
must be used to obtain these port rates. To oversample, the
Async!Sync configuration option must be disabled and
the synchronous port rate must be set to a rate greater than
or equal to four times the asynchronous DTE rate. For
example, select 1.2 kbps for the synchronous port speed if
the asynchronous port speed is 150 or 300 bps, select
2.4 kbps if it is 600 bps, and 7.2 bps if it is 1800 bps. This
ensures that oversampling will take place.
Figure 4-4. Single-Port Point-to-Point Circuit with Nondisruptive Diagnostics