TIME SLOT INTERCHANGE
DIGITAL SWITCH
256 x 256
IDT728985
andwriteaccess toindividualchannels.As animportantfunctionofadigital
switchis tomaintainsequenceintegrityandminimizethroughputdelay,the
IDT728985isanidealsolutionformostswitchingneeds.
ꢀEATURES:
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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
(P-DIP)
ꢀUNCTIONALDESCRIPTION
Framesequence,constantthroughputdelay,andguaranteedminimum
delayarehighpriorityrequirementsintoday’sintegrateddataandmultimedia
networks. TheIDT728985provides thesefunctions onaper-channelbasis
usingastandardmicroprocessorcontrolinterface. Eachoftheeightseriallines
is designed to switch 64 Kbit/s PCM or N x 64 Kbit/s data.
InProcessorMode,themicroprocessorcanaccesstheinputandoutputtime
slotstocontrolotherdevicessuchasISDNtransceiversandtrunkinterfaces.
SupportingbothGCIandST-BUS® formats,IDT728985hasincorporatedan
internal circuit to automatically identify the polarity and format of the frame
synchronization.
DESCRIPTION:
TheIDT728985isaST-BUS®/GCIcompatibledigitalswitchcontrolledby
amicroprocessor. TheIDT728985canhandleasmanyas256,64Kbit/sinput
andoutputchannels. Those256channelsaredividedinto8serialinputsand
outputs,eachofwhichconsistsof32channels. TheIDT728985providesper-
channelvariableorconstantthroughputdelaymodesandmicroprocessorread
AfunctionalblockdiagramoftheIDT728985deviceisshownonpage1.
The serial streams operate continuously at 2.048 Mb/s and are arranged in
125µswideframeseachcontaining32,8-bitchannels. Eightinput(RX0-7)and
ꢀUNCTIONAL BLOCK DIAGRAM
ODE
C4i
F0i
VCC GND
TX0
TX1
TX2
TX3
TX4
TX5
TX6
TX7
Timing
Unit
RX0
RX1
RX2
RX3
RX4
RX5
RX6
RX7
Output MUX
Receive
Serial Data
Streams
Transmit
Serial Data
Streams
Data
Memory
Connection
Memory
Control Register
Microprocessor Interface
5708 drw01
CCO
DS
A0/
A5
CS
R/W
D0/
D7
DTA
APRIL 2001
1
2001 Integrated Device Technology, Inc.
DSC-5708/2