Vocality V100 Technical Manual page 66

C H A P T E R 3 C O N F I G U R I N G V 1 0 0
MODE
Data channels may operate in one of two basic modes, either as an aggregate port or as a tributary
channel. An aggregate port performs the function of multiplexing a number of tributary connections over a
carrier service to a remote unit. The V100 is capable of operating multiple aggregate ports.
When a TDM card is fitted, it is then possible to nominate data ports to operate as TDM channels by
selecting "TDM" mode. These channels are still tributary ports but the data is not packetised; instead it
passes over a timeslot in the frames being transmitted by the TDM card.
TYPE
The port type field allows the user to select the correct circuit presentation for the data port. When DTE
type is selected, the port is configured as Data Terminating Equipment and may be logically connected
using a straight cable to modems, for example (which are normally DCE). In other words, the TXD signal
is an output from the V100 and should be connected to the TXD pin on the modem, which is an input.
When DCE is selected, all of the signals reverse direction and the port is configured as Data Circuit
terminating Equipment and may be logically connected using a straight cable to terminals, for example.
The TXD signal is now an input to the V100 and should be connected to the TXD pin on the PC, which is
an output. The changeover is performed under software control and no jumper links need to be changed
internally.
FORMAT
The format field is used to specify the kind of data to be transferred by the port. If synchronous, then
transparent (SYNC) or NRZ framed data may be selected, or if async then the specific word structure is
selected. The format must be the same at both ends of the multiplexer link.
In async modes an additional parameter is accessible immediately to the right of the main format entry
which consists of a single character. This allows the user to select from Raw, Error-corrected or
Compressed operation (Raw is selected by default). See section 4.10 "Async Error-correction and
Compression" for details.
CLOCK SETTINGS
The V100 offers independent RX and TX clocks on every port and each one has three settings controlling
rate, source and reference. The convention used is that the RX clock is associated with the direction of
data from the aggregate to the tributary, whereas the TX clock is associated with the flow of data from
the tributary to the aggregate. The clock source defines where the clock physically comes from. The
reference field defines whether that clock is used as a reference by the unit or if instead the unit generates
the clock using one of the two internal busses as a reference. When the clock is generated by the unit, the
rate field must be specified. For external ("EXT") or looped clocks, it may be left blank.
V100 Versatile Multiplexer Technical Manual Version 2.2
Page 66 of 231