cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 21

• Manufacturer Part Number: cx28500
• Description: Cx28500 Multichannel Synchronous Communications Controller
• Manufacturer: Mindspeed Technologies

addresses) allows any number of VSPs to be concatenated into a single logical channel. This concatenation allows
mixed VTG path options without changing the number of time slots assigned to the TSBUS port. In the TSBUS
transmit direction, CX28500 requires the stuff status for each time slot to be presented at its TSTUFF input exactly
8 time slots in advance of the actual time slot for which the stuff status is applied. The amount of the TSTUFF
advance is fixed at 8 time slots even though the number of time slots within a frame might vary. For the receive
direction CX28500 requires the stuff status for each time slot to be presented at its RSTUFF input on the current
time slot for which the stuff is applied (For a detailed description, see the timing diagrams in
1.4
Independent of the particular layering scheme used, or the functions of the layers, the operation of layered
protocols is based on the fundamental idea of a layering principle (refer to
Level 2 of the protocol stack specifies how data travels between a Host and the packet switch to which it connects.
Because raw hardware delivers only a stream of bits, the level 2 protocol must define the format of frames and
specify how the machines recognize frame boundaries. This function is one of CX28500’s features, including error
detection (e.g., a frame checksum). Usually, protocols use the term “frame” to refer to a unit of data as it passes
between a Host and a packet switch.
CX28500, as a high-throughout communications controller for synchronous or asynchronous path applications,
multiplexes and demultiplexes up to 1024 data channels and allows upper protocols to recognize frame boundaries
and check if a frame has been transferred successfully. Examples of CX28500’s potential applications as a layer 2
protocol device and examples of device communication with other upper layers are described in
Figure 1-1.
28500-DSH-002-C
CX28500 as a Data Link Layer Device
CX28500 Layering Model
- HSSI
- SONET/SDH
- T3/E3
- T1/E1
- X.25
- MODEMS/DSL
Physical
Layer
Mindspeed Proprietary and Confidential
Mindspeed Technologies
EBUS
Highway
TSBUS
PCM
- Variable speed per
- Variable number of
- Variable number of
- Variable number of
CX28500 Features
channel port
time slots per port
channels per port
time slots per logical channel
Layer
Link
®
PCI
Figure
- Packet switch
- Cell switch
- Processor
1-1).
Upper
Layer
500052_078
Appendix
Section
Introduction
E.)
1.5.
6