TIME SLOT INTERCHANGE
256 x 256
• 256 x 256 channel non-blocking switch
• Automatic signal identification (ST-BUS®, GCI)
• 8 RX inputs — 32 channels at 64 Kbit/s per serial line
• 8 TX outputs — 32 channels at 64 Kbit/s per serial line
• Three-state serial outputs
• Microprocessor Interface (8-bit data bus)
• Frame Integrity for data applications
• 5V Power Supply
• Operating Temperature Range -40°C to +85°C
• Available in 44-pin Plastic Leaded Chip Carrier (PLCC),
44-pin Plastic Quad Flatpack (PQFP) and 40-pin Plastic Dip
The IDT728985 is a ST-BUS®/GCI compatible digital switch controlled by
and output channels. Those 256 channels are divided into 8 serial inputs and
channel variable or constant throughput delay modes and microprocessor read
and write access to individual channels. As an important function of a digital
switch is to maintain sequence integrity and minimize throughput delay, the
IDT728985 is an ideal solution for most switching needs.
Frame sequence, constant throughput delay, and guaranteed minimum
delay are high priority requirements in today’s integrated data and multimedia
networks. The IDT728985 provides these functions on a per-channel basis
is designed to switch 64 Kbit/s PCM or N x 64 Kbit/s data.
In Processor Mode, the microprocessor can access the input and output time
slots to control other devices such as ISDN transceivers and trunk interfaces.
Supporting both GCI and ST-BUS® formats, IDT728985 has incorporated an
internal circuit to automatically identify the polarity and format of the frame
A functional block diagram of the IDT728985 device is shown on page 1.
The serial streams operate continuously at 2.048 Mb/s and are arranged in
.UNCTIONAL BLOCK DIAGRAM
C4i F0i VCC GND
Unit Output MUX
RX3 Serial Data
RX4 Streams Memory
RX7 Microprocessor Interface
DS CS R/W A0/ DTA D0/
2001 Integrated Device Technology, Inc.