GatesAir Intraplex DS-64NC, Installation And Operation Manual

Page: 15 / 68

2 – Functional Description DS-64NC Synchronous Data Module
Version 9.1
GatesAir 2-3
Intraplex Products
2.3 Time Slot Assignment
The module may be placed in either of two modes: 7 bits per time slot (56xN kbps) or 8 bits per time
slot (64xN kbps). In the 7-bit mode, the 8th bit is set to “1” and is monitored for errors at the receive
side (Section 2.5). You specify the starting time slot number and whether adjacent or alternate time
slots are to be used.
Normally, adjacent time slots are used, but certain sub-rate services require the use of alternate time
slots. Also, you can use an alternate time slot assignment to solve ones-density problems in 64xN
systems when the payload includes other kinds of channels that can be interleaved with the data from
this module. Wrap-around of time slot assignments is not allowed; if the starting time slot is set too
high for the requested data rate, the module does not operate. In 2 MB applications, you can skip time
slot 16 to allow for CAS signaling.
2.4 Loopbacks
Loopbacks connect the data and timing signals from one direction to the other direction in place of the
payload. The DS-64NC module provides three types of loopbacks:
●
Local (payload)
● Equipment
● Remote
Loopbacks do not force the module into full-duplex operation if the module is not operating in full-
duplex already. In a half-duplex configuration, a local (payload) loopback works, but an equipment
loopback does not.
Figure 2-2. Loopbacks
2.4.1 Local (Payload) Loopback
A local (payload) loopback exercises channel module logic up to the bus interface. Incoming data from
the RS-449 or V.35 port is looped back to the same port. This loopback may only be activated at the
near end (by switch or remotely). A local loopback is activated in the module at Location 1 (Figure 2-
2). Receive timing becomes frequency-locked to transmit timing. This loopback type is used to check
the performance of the module itself.
2.4.2 Equipment Loopback
An equipment loopback turns receive-side data around to the transmit side at the line interface from
the near end (Figure 2-2). If the backplane buses in the shelf are not frequency-locked when the
equipment loopback is in effect, the transmit-side FIFO spills periodically.