Functional Units - AT&T MERLIN LEGEND Installation & Maintenance Manual

System Description

Functional Units

The functional units are the processor module, which controls the
operation of the system and its features; the line/trunk and station
modules, which connect the central office (CO) lines/trunks to
the stations; the power supply module, which supplies power to
the control unit; and the carrier with its backplane assembly,
which contains the input/output (I/O) bus and the time-division
multiplex (TDM) bus. All the modules are electrically connected
to the backplane, which provides common circuitry for the I/O
bus, the TDM bus, and power distribution. (See Figure 10 for a
functional block diagram of the system architecture.)
The processor module is connected to intelligent ports on the
line/trunk and station modules, through the I/O bus, by the digital
switch element (DSE) on each line/trunk and station module. The
TDM bus also is connected to the DSE of each line/trunk and
station module. The two busses are described below:
Input/Output Bus. The I/O bus contains a 16-bit address bus
and an 8-bit data bus. The address bus selects the module
that receives instructions from the 68000 microprocessor in
the processor module. The microprocessor provides
instructions to the port processors and DSEs through the 8-bit
data bus.
Time-Division Multiplex Bus. The TDM bus connects the
DSEs to allow voice or data to flow in and out of the system.
The TDM bus is parallel, 8 bits wide, and runs at 2.048 MHz
(256 time slots x 8 kHz = 2.048 MHz). Each TDM cycle has
256 time slots for voice, data, tones, and clocks. The frame
repetition rate is 8 kHz, providing a 64-kbps channel on each
time slot (8-bit bus x 8 kHz = 64 kbps).
Functional Units 1-45