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IDT72V8981 Datasheet(PDF) 4 Page - Integrated Device Technology

Part No. IDT72V8981
Description  3.3 VOLT TIME SLOT INTERCHANGE DIGITAL SWITCH 128 x 128
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Maker  IDT [Integrated Device Technology]
Homepage  http://www.idt.com
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IDT72V8981 Datasheet(HTML) 4 Page - Integrated Device Technology

 
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Commercial Temperature Range
IDT72V8981 3.3V Time Slot Interchange
Digital Switch 128 x 128
is split into two 8-bit blocks—Connection Memory HIGH and Connection
Memory LOW. Each location in Connection Memory is associated with a
particularchannelinanoutputstreamsoastoprovideaone-to-onecorrespon-
dencebetweenConnectionandDataMemories. Thiscorrespondenceallows
for per channel control for each TX output stream.
In Processor Mode, data output on the TX is taken from the Connection
Memory Low and originates from the microprocessor (Figure 2). Where as in
ConnectionMode(Figure1),dataisreadfromDataMemoryusingtheaddress
in Connection Memory. Data destined for a particular channel on the serial
output stream is read during the previous channel time slot to allow time for
memory access and internal parallel-to-serial conversion.
CONNECTION MODE
In Connection Mode, the addresses of input source for all output channels
are stored in the Connection Memory Low. The Connection Memory Low
locationsaremappedtocorresponding8-bitx32-channeloutput. Thecontents
oftheDataMemoryattheselectedaddressarethentransferredtotheparallel-
to-serial converters. By having the output channel to specify the input channel
through the Connection Memory, input channels can be broadcast to several
outputchannels.
PROCESSOR MODE
InProcessorModetheCPUwritesdatatospecificConnectionMemoryLow
locations which are to be output on the TX streams. The contents of the
ConnectionMemoryLowaretransferredtotheparallel-to-serialconverterone
channelbeforeitistobeoutputandaretransmittedeachframetotheoutputuntil
it is changed by the CPU.
CONTROL
The Connection Memory High bits (Table 4) control the per-channel
functions available in the IDT72V8981. Output channels are selected into
specific modes such as: Processor mode or Connection mode and Output
Drivers Enabled or in three-state condition.
OUTPUT DRIVE ENABLE (ODE)
The ODE pin is the master three-state output control pin. If the ODE input
is held LOW all TX outputs will be placed in high impedance regardless
ConnectionMemoryHighprogramming.However,ifODEisHIGH,thecontents
of Connection Memory High control the output state on a per-channel basis.
DELAY THROUGH THE IDT72V8981
The transfer of information from the input serial streams to the output serial
streams results in a delay through the device. The delay through the
IDT72V8981 device varies according to the combination of input and output
streams and the movement within the stream from channel to channel. Data
receivedonaninputstreammustfirstbestoredinDataMemorybeforeitissent
out.
As information enters the IDT72V8981 it must first pass through an internal
serial-to-parallel converter. Likewise, before data leaves the device, it must
passthroughtheinternalparallel-to-serialconverter. Thisdatapreparationhas
an effect on the channel positioning in the frame immediately following the
incoming frame—mainly, data cannot leave in the same time slot. Therefore,
information that is to be output in the same channel position as the information
is input, relative to the frame pulse, will be output in the following frame.
Whether information can be output during a following timeslot after the
informationenteredtheIDT72V8981dependsonwhichRXstreamthechannel
information enters on and which TX stream the information leaves on. This is
causedbytheorderinwhichinputstreaminformationisplacedintoDataMemory
and the order in which stream information is queued for output. Table 1 shows
the allowable input/output stream combinations for the minimum two channel
delay.
SOFTWARE CONTROL
If the A5 address line input is LOW then the IDT72V8981 Internal Control
Register is addressed. If A5 input line is high, then the remaining address input
linesareusedtoselectthe32possiblechannelsperinputoroutputstream. The
address input lines and the Stream Address bits (STA) of the Control register
give the user the capability of selecting all positions of IDT72V8981 Data and
Connection memories. The IDT72V8981 memory mapping is illustrated in
Table 2 and Figure 3.
The data in the control register (Table 3) consists of Memory Select and
Stream Address bits, Split Memory and Processor Mode bits. In Split Memory
mode (Bit 7 of the Control register) reads are from the Data Memory and writes
are to the Connection Memory as specified by the Memory Select Bits (Bits 4
and 3 of the Control Register). The Memory Select bits allow the Connection
Memory HIGH or LOW or the Data Memory to be chosen, and the Stream
Address bits define internal memory subsections corresponding to input or
outputstreams.
The Processor Enable bit (bit 6) places EVERY output channel on every
output stream in Processor mode; i.e., the contents of the Connection Memory
LOW(CML,seeTable5)areoutputontheTXoutputstreamsonceeveryframe
unless the ODE input pin is LOW. If PE bit is HIGH, then the IDT72V8981
behaves as if bits 2 (Channel Source) and 0 (Output Enable) of every
ConnectionMemoryHigh(CMH)locationsweresettoHIGH,regardlessofthe
actual value. If PE is LOW, then bit 2 and 0 of each Connection Memory High
locationoperatesnormally. Inthiscase,ifbit2oftheCMHisHIGH,theassociated
TX output channel is in Processor Mode. If bit 2 of the CMH is LOW, then the
contents of the CML define the source information (stream and channel) of the
time slot that is to be switched to an output.
If the ODE input pin is LOW, then all the serial outputs are high-impedance.
IfODEisHIGH,thenbit0(OutputEnable)oftheCMHlocationenables(ifHIGH)
or disables (if LOW) the output stream and channel.
5702 drw06
TX
Microprocessor
Receive
Serial Data
Streams
Transmit
Serial Data
Streams
Data
Memory
Connection
Memory
Receive
Serial Data
Streams
5702 drw05
RX
TX
Transmit
Serial Data
Streams
Data
Memory
Connection
Memory
Figure 2. Processor Mode
Figure 1. Connection Mode
FUNCTIONAL DESCRIPTION (Cont'd)


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