Welltech SPCI2S Intel NetStructure SS7 Boards - Manual (Page 24)

SS7 Programmer’s Manual for SPCI2, SPCI4 and CPM8 Issue 2 Page 24
3.4 Using the CT bus
3.4.1 Introduction
The SPCI2S, SPCI4 and CPM8 cards support two, four or eight E1/T1 Line
Interface Units and a CT bus interface (H.100 or H.110). The on-board signalling
processor handles the SS7 signalling timeslots whilst the remaining circuits (voice
or data bearer circuits) are passed to the CT bus for distribution to other cards.
All communication between the application and the board is message based. Initial
configuration is usually handled by the configuration utility s7_mgt, which takes
commands from the text file (config.txt) and generates all the necessary
configuration messages for the board. Subsequent operation is entirely message
driven, messages being passed in both directions between the board and the
application.
One of the roles of the application is to control the dynamic switching between the
CT bus and the E1 / T1 line interfaces. This section provides details of how to
interface with the CT bus, including the initial (static) configuration and the
subsequent (dynamic) switching.
The operation of the CT bus switching interface is described in terms of the SCbus
switching model using the messages MVD_SC_DRIVE_LIU,
MVD_MSG_SC_LISTEN and MVD_MSG_SC_FIXDATA and config.txt commands
LIU_SC_DRIVE and SCBUS_LISTEN.
3.4.2 Switching Model
The basic switching model assumes that at system initialisation all incoming E1/T1
timeslots and all resource card output timeslots are connected up to channels on
the CT bus and that these connections are never changed. This has the advantage
that once the on-board CT bus drivers have been set up they are never changed so
the chances of inadvertently causing CT bus conflict is minimised. It also means
that the user can predict the exact CT bus channels where any input timeslot can
be located and this in turn can assist with fault diagnosis and general system test.
It is also possible to generate fixed patterns on any E1/T1 output timeslots to
provide the correct idle pattern for presentation to the network on all circuits where
there is no active call.
NOTE: Generation of fixed patterns to the network is handled differently to the
method used on the PCCS6 card which involved generating a fixed pattern on an
SCbus channel and connecting it through the switch towards the E1/T1 interface.
This is due in part to increased functionality available on the CT bus interface
hardware and in part due to a lack of available channels for use in generating a
pattern on the CT bus.
Having completed the system initialisation all drives to the CT bus are set up. Then
on a dynamic (call by call) basis, the connectivity must be modified when a new call
arrives and when it finishes.