cx28560 Mindspeed Technologies, cx28560 Datasheet - Page 87

• Manufacturer Part Number: cx28560
• Description: Hdlc Controller
• Manufacturer: Mindspeed Technologies

CX28560 Data Sheet
4.7.7
28560-DSH-001-B
TSBUS Interface
The TSBUS is a time slot interface. The digital communication data paths and
overhead channels consist of payload data and overhead data derived from either
SONET or SDH data streams, and payload and overhead data derived from either
electrical DS3 or E3 data streams. One of the overhead channels may consist of
HDSL messages generated and received by the Command Status Processor
(CSP). The messages are provided by the local processor that is connected to
access and configure local device registers. The TSBUS interface is capable of
full-duplex (bi-directional) transmission of data between one device and the
CX28560 device. The interface consists of two, 1-bit wide serial interfaces: a bi-
directional payload TSBUS and bi-directional overhead TSBUS.
A TSBUS frame structure is defined as an integer multiplication of bytes. A
TSBUS port can be either DS0 extraction (group extraction and synchronization
is performed) or non-DS0 extraction (group extraction and synchronization is not
performed).
When a port is defined as TSBUS non-DS0 extraction, its interface is defined by
seven signals. When a port is defined as TSBUS DS0 extraction, its interface is
defined by nine signals—the standard seven signals from the non-DS0 extraction
mode, and an extra two group synchronization signals.
In the TSBUS mode, the Rx and Tx are synchronous (i.e., the first bit of Tx and
Rx frame is sampled on the falling or rising edge of RCLK/TCLK on TDAT/
RDAT). TSTB defines the frame synchronization, which marks the first bit of the
Rx/Tx frame. TSTUFF acts as a flow control signal that indicates “stuff ” (update)
to be sent on the following time slot mapped to the logical channel. TSTUFF is
sampled in the first two bits of the channel’s time slot.
In the TSBUS transmit direction, the CX28560 requires the stuff status for each
time slot to be presented at its TSTUFF input exactly eight 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 eight time slots even though the number of time slots
within a frame might vary. In DS0 extraction mode, an extra signal (TGSYNC)
performs group synchronization.
For the receive direction, CX28560 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. In DS0 extraction mode, an extra signal (RGSYNC) performs group
synchronization.
Mindspeed Technologies™
Advance Information
CX28560 Serial Interface
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