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2.2 Characteristics

You need to understand the following characteristics of the CT Access Switching service as you prepare to create an application:

2.2.1 Switch Handles

Many functions take (or return) a switch handle. A switch handle identifies an open MVIP switching device.

To access an MVIP switching device, get a switch handle by calling swiOpenSwitch. Refer to Section 3.2, Opening a Switch Handle.

swiCloseSwitch releases a switch handle. Refer to Section 3.3, Closing a Switch Handle.

2.2.2 Terminus

A terminus is a single access point to a switch block input or switch block output. Many of the Switching service functions take one or more terminus elements as an argument.

A terminus contains a bus, a stream, and a timeslot:

Component

 Description

Bus

 Specifies the interface point of the switch block. Devices can reside directly on the telephony bus. Devices can also reside on a board's local bus and may require a switch block to access the telephony bus.

Stream

 Specifies a grouping of timeslots that usually corresponds to a particular bit-stream of time-division multiplexed (TDM) serial data on an individual track or wire of a bus.

Timeslot

 Specifies a particular 64 kbit/second subdivision of a TDM bus stream. Timeslots number from zero (0) to n where n is stream-dependent.

2.2.3 MVIP-95 Switch Block Model

In the MVIP-90 switch model, the 16 MVIP data streams are addressed as streams 0..15, and local resources start at stream 16. Since the H-MVIP bus has 24 data streams and the H.100 bus has 32 data streams, the MVIP-95 switch model was created to accommodate the additional data streams.

The MVIP-95 switch model is used with the MVIP-90, H-MVIP, and H.100 busses. The MVIP-95 model is based on the premise that a given stream number corresponds to the same physical wire on both sides of the switch block.

As illustrated in Figure 2, the MVIP-90 convention for numbering the bus signals was to number each bus signal with two numbers, one for the input side of the switch block and the other number for the output side of the switch block. For example, on the input side of the switch block, the bus signals DSo0 through DSo7 correspond to streams 0 through 7. On the output side of the switch block, the bus signals DSo0 through DSo7 correspond to streams 8 through 15.

Figure 2. The MVIP-90 Switch Block Model



As illustrated in Figure 3, this was simplified in MVIP-95 by using one number to number each bus signal, regardless of the side of the switch block. In MVIP-95, bus signals are numbered sequentially starting at 0. This allows for future expansion of the switch capacity without renumbering.


 



Figure 3.	 The MVIP-95 Switch Block Model




For example, in MVIP-95, the MVIP bus signal DSo0 (H.100 bus signal HDS0) is numbered 0 regardless of which side of the switch block is connected to the signal.



In MVIP-90, local devices are connected to streams 16 and higher. In MVIP-95, local devices are connected to a logical bus called a local bus. The streams they are connected to are numbered sequentially starting from 0 on the local bus. 



In MVIP-95, both MVIP streams and local streams are numbered sequentially starting from 0. Therefore, there is a need to explicitly specify the bus when referring to a switch block input or output. MVIP-95 defines a new data structure called a terminus that contains a bus specifier, a stream number, and a timeslot number to refer to a switch block input and output.



Refer to the Getting Started With MVIP Switching Manual for more information about the switch block models.



Figure 4 shows the mapping of mapping of MVIP-90 streams to MVIP-95 streams.


 



Figure 4.	 Mapping of MVIP-90 Streams to MVIP-95 Streams








 
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