8/9/2019 C-DOT Arch

1/53

CDOT

Centre for Development of

Telematics is a Telecom Technologydevelopment centre of GOI, estd.

in1984. Main objective is to build a

centre for excellence in the area ofTelecom Technology & to design,

develop digital exchanges in India.

RTTC, HYD

8/9/2019 C-DOT Arch

2/53

2

INTRODUCTIONC-DOT DSS MAX is a universal digital switch, which

can be configured for different applications as local,

transit, or integrated local, and transit switch.

High traffic/load handling capacity upto 8,00,000

BHCA with termination capacity of 40,000 Lines as

Local Exchange or 15,000 trunks as Trunk Automatic

Exchange, the C-DOT DSS family is ideally placed to

meet the different requirements of any integrated digital

network.

8/9/2019 C-DOT Arch

3/53

3

BASIC GROWTH/BUILDING MODULES

C-DOT DSS MAX exchanges can be configured using

four basic modules

Base Module

Central Module

Administrative Module

Input Output Module

8/9/2019 C-DOT Arch

4/53

4

8/9/2019 C-DOT Arch

5/53

5

BASE MODULE

The Base Module (BM) is the basic growth unit of the

system. It interfaces subscriber lines, analog and digital

trunks, CCM and PBX lines. Each Base Module caninterface upto 2024 terminations. The number of Base

Modules directly corresponds to the exchange size. It

carries out majority of call processing functions and, in a

small-exchange application, it also carries out operation

and maintenance functions with the help of the InputOutput Module.

8/9/2019 C-DOT Arch

6/53

6

In Single Base Module (SBM) exchange configuration,

the Base Module acts as an independent switching systemand provides connections to 1500 lines and 128 trunks. In

such a configuration, the Base Module directly interfaces

with the Input Output Module for bulk data storage,

operations and maintenance functions. Clock andsynchronization is provided by a source within the Base

Module. It is a very useful application for small urban and

rural environments.

With minimum modifications in hardware through onlyone type of card, a Base Module can be remotely located

as a Remote Switch Unit (RSU), parented to the main

exchange using PCM links

8/9/2019 C-DOT Arch

7/53

7

CENTRAL MODULE

Central Module (CM) consists of a message switch

and a space switch to provide inter-module

communication and perform voice and data switching

between Base Modules. It provides control messagecommunication between any two Base Modules, and

between Base Modules and Administrative Module for

operation and maintenance functions. It also provides

clock and synchronization on a centralized basis.

8/9/2019 C-DOT Arch

8/53

8

ADMINISTRATIVE MODULE

1. Administrative Module (AM) performs system-level

resource allocation and processing function on a

centralized basis.

2. AM performs all the memory and time intensive callprocessing support functions and also administration

and maintenance functions.

3. AM communicates with the Base Module via the

Central Module. It supports the Input Output Module

for providing man- machine interface. It also supports

the Alarm Display Panel for the audio-visual indication

of faults in the system.

8/9/2019 C-DOT Arch

9/53

9

INPUT OUTPUT MODULE (I0M)

Input, Output Module (IOM) consists of duplicated Input Output

Processor (IOP). It is used as the front-end processor in C-DOT DSS. It

handles all the input and output functions in C-DOT DSS. The IOP is

connected to AP/BP via HDLC links.

During normal operation, two IOPs interconnected by a HDLC link,operate in a duplex configuration. Working as front-end processor, it

provides initial code down load to the subsystems, man machine

interface and data storage for billing and other administrative

information.

IOP interfaces various secondary storage devices like' disk drives,cartridge tape drive and floppy drive. It supports printers and upto 8

serial ports for video display units which are used for man- machine

communication interface. All the bulk data processing and storage is

done in this module

8/9/2019 C-DOT Arch

10/53

10

REMOTE SWITCH UNIT

Remote Switch Unit (RSU) is an integral part of C-DOTDSS architecture. In order to realise a RSU, the normalBM can be modified for remoting with the host exchangevia 2 Mbps digital links.

The number of 2 Mbps links between the MainExchange and RSU is primarily determined by the traffic.A maximum 16 PCMs can be provided between a RSU& Main exchange.

Analog and Digital trunk interfaces are also implemented

in RSU to support direct parenting of small exchangesfrom RSU itself instead of parenting it to the mainexchange which will ultimately save the media requiredfrom main exchange

8/9/2019 C-DOT Arch

11/53

11

RSU contnd

RSU is an autonomous exchange capable of local-callcompletion. Operation and maintenance functions arehandled by the host exchange. In the event of failure ofPCM links, RSU goes into standalone mode of operation.In case it is not possible to process a call request due to

unavailability of links to the host, the subscriber isconnected to appropriate tone or announcement.

During standalone mode of operation, the local andIncoming terminating calls in RSU are switched and themetering information of all the RSU subscribers is stored

in the RSU. It is sent to the host whenever the PCM linksare available again. Only the even numbered BMs can beconfigured as RSU i.e. a maximum 16 RSUs are possiblein C-DOT DSS MAX-XL and 8 RSUs in MAX-L.

8/9/2019 C-DOT Arch

12/53

12

COMMON CHANNEL SIGNALLING NO. 7 AND ISDN

Common Channel Signalling is pre-requisite to

provide any value added service in the networke.g. IN Services, ISDN services. Due to intelligentprotocol implementation in conformance to ITU-Tspecifications and with the implementation ofCCS7 signalling in C-DOT DSS, it has been made

possible to provide the value added services andalso as TAX exchange with multiple nodes,connected on CCS7 signalling.

ISDN Services are the most widely used carriers

to transport bulk volume of data. With theincreasing use of Internet Access, the use of ISDNinterface is likely to go up as it provides thereliable access to the user at the rate of 64/128Kbps. In addition to reliable data connection at

higher rate, it integrates computer and Telephoneon the single access.

8/9/2019 C-DOT Arch

13/53

13

REDUNDANCY

To meet the stringent availability requirements, C-DOTDSS employs 'hot standby' technique for all processorcomplexes so that in the event of the failure of any onesecurity-block, not more than 8 subscribers will be affected.

Hardware cross-links between processors have been planned in such a way that even the failure of twodissimilar processors will not affect system performance.Also, wherever there is no duplication of hardware units,multiple units are provided to work in a load-sharing mode.

In the event of failure of one of the units, other units willshare its load preventing disruption of service. In case ofcertain service circuits, n+1 configuration is used formaintaining reliability.

8/9/2019 C-DOT Arch

14/53

14

HARDWARE ARCHITECTURE

Analog Terminal Unit- to interface analog lines/trunks,

and providing special circuits as conference,announcements and terminal tester.

Digital Terminal Unit- for interfacing digital trunks i.e.2Mbps E-1/PCM links

Signalling Unit Module - to support SS7 protocol handlersand some call processing functions for CCS7 calls.

ISDN Terminal Unit- to support termination of BRI/PRIinterfaces and implementation of lower layers of DSS1signalling protocol.

Time Switch Unit- for voice and message switching andprovision of service circuits.

Base Processor Unit- for control message communicationand call processing functions.

8/9/2019 C-DOT Arch

15/53

15

Analog Terminal Unit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

P

S

U

I

T

C

T

C

T

C

T

C

T

C

T

C

T

C

T

C

T

I

C

S

P

C

/

I

S

P

T

U

I

T

U

I

T

I

C

S

P

C

/

I

S

P

T

C

T

C

T

C

T

C

T

C

T

C

T

C

T

C

P

S

U

I

8/9/2019 C-DOT Arch

16/53

16

Analog Trunk Cards Analog trunk cards interface analog inter-

exchange trunks which may be of three

types as TWT, EMT and EMF. These

interfaces are similar to Subscriber Line

Card, with only difference that the

interfaces are designed to scan/drive eventson the trunks as per predefined signalling

requirement.

8/9/2019 C-DOT Arch

17/53

17

Analog Subscriber Line Cards

Two variants of subscriber line cards as LCC or CCM withinterfaces up to 8 subscribers, provide basic BORSCHTfunctions for each line. Analog to digital conversion isdone by per-channel CODEC according to A-law ofPulseCode Modulation. Each CCM card has the provision of

battery reversal for all the 8 lines with the last two lines

having provision to generate 16 KHz metering pulses to besent to subscriber's metering equipment.

The 8-bit digital (voice) output of four LCCs ismultiplexed to form a 32- channel, 2 Mbps PCM link - alsocalled a terminal group (TG). Since a Terminal Unit has amaximum of 16 terminal cards, there are four suchterminal groups. The signalling information is separated bya scan/drive logic circuit and is sent to the signalling

processor on four different scan/drive signals. TheLCC/CCM also provides test access relay to isolate theexchange side and line side to test it separately by using

the Terminal Test Controller (TTC).

8/9/2019 C-DOT Arch

18/53

18

Signalling Processor Card

Signalling Processor (SP) processes the signallinginformation received from the terminal cards. Thissignalling information consists of scan/drive functions

like origination detection, answer detection, digitreception, reversal detection, etc. The validated eventsare reported to Terminal Interface Controller for further

processing to relieve itself from real-time intensivefunctions. Based on the information received from the

Terminal Interface Controller, it also drives the event onthe selected terminal through scan/drive signals.

8/9/2019 C-DOT Arch

19/53

19

TERMINAL INTERFACE CONTROLLER

Terminal Interface Controller (TIC) controls the fourterminal groups (TG) of32 channels, and multiplex them toform a duplicated 128-channel, 8 Mbps link towards theTime Switch (TS). For signalling information of 128-

channels, it communicates with Signalling Processor (SP) toreceive/send the signalling event on analog terminations. Italso uses one of the 64 kbps channel out of 128 channelstowards Time Switch, to communicate with Base ProcessorUnit (BPU). In concentration mode, three other TerminalUnits share this 128-channel link towards the Time Switchto have 4:1 concentration. Terminal Interface Controller is

built around 8-bit microprocessor with associated memoryand interface and it is duplicated for redundancy.

8/9/2019 C-DOT Arch

20/53

20

8/9/2019 C-DOT Arch

21/53

21

TIC Functions

Provides voice interface of the terminals

with time switch,

Receives scan signalling information for the

terminals passes it to BP. Also it gets the

messages from BP to drive events on the

terminals and passes the corresponding

drive command to SP.

Keeps on doing diagnostics on the cardspresent in TU periodically and keeps on

informing the BP through HDLC messages.

8/9/2019 C-DOT Arch

22/53

22

TIC Functions contnd

Voice interface with TCs

TIC multiplexes the four2 Mbps links andpresents the digitized speech of 128 terminals on a

128 time slot, 8 Mbps serial link towards Time

Switch. TIC can place voice of any of the 128

terminals on any of these time slots 1-127 towardsthe Time switch and vice versa.

Speech info from Exchange towards Terminals

TIC receives 128 time slot, 8 Mbps link from TS

and de-multiplex it in to 4 links of2Mbps ( 32

Time slots) towards the TGs.

8/9/2019 C-DOT Arch

23/53

23

TIC Functions contnd

Signaling Interface with SP

a) When TIC receives a new signalling event fromSP, it informs BP about the event. This

information is sent by TIC in HDLC format in

TS0 of 128 TS, 8Mbps link towards the TS.

During an event on a Terminal

Whenever, BP wants to drive any event on a

terminal, BP sends corresponding message to TIC

through nailed up path. TIC receives it in TS0 of

128 TS, 8Mbps link from TS. Then TIC writes the

event and the terminal circuit number in SP

memory.

8/9/2019 C-DOT Arch

24/53

24

Special Service Cards

A Terminal Unit has some special service cards such asConference (CNF) Card to provide six party conference.Speech samples from five parties are added by inbuilt logicand sent to the sixth party to achieve conferencing.

Terminal Test Controller (TTC) Card is used to test

analog terminal interfaces via the test access relays on theterminal cards.

Announcement Controller (ANN) Card provides 15announcements on broadcast basis. Only one service cardof each type is equipped in a Base Module with provisionof fixed slot for TTC and variable slots for CNF/ANNC.

Announcement and Conference Cards are equipped inTerminal Unit through S/W MMC command. Two slotsare occupied by each card i.e. 16 channels for each card areused out of 128 channels available on a Bus between a TU& TS.

8/9/2019 C-DOT Arch

25/53

25

Digital Terminal Unit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

P

SU

I

D

TS

0

D

TC

0

D

TS

1

D

TC

1

T

U

C

T

U

I

T

U

I

T

U

C

D

TS

2

D

TC

2

D

TS

3

D

TC

3

P

SU

I

8/9/2019 C-DOT Arch

26/53

26

Digital Terminal Unit (DTU)

Digital Terminal Unit (DTU) is used exclusively tointerface digital trunks. One set of Digital TrunkSynchronization (DTS) card along with the Digital TrunkController (DTC) card is used to provide one E-1 interface.

Each interface occupies one TG of32 channels and four

such interfaces share 4 TGs in a Digital Terminal Unit. The functions performed by TIC and SP in AnalogTerminal Unit, are collectively performed by the TerminalUnit Controller (TUC) in the Digital Terminal Unit.

The scan functions are - HDB3 to NRZ code conversion,

frame alignment and reconstitution of the received frame. The drive functions include insertion of frame alignment

pattern and alignment information. Each interface can beconfigured as CAS or CCS interface.

8/9/2019 C-DOT Arch

27/53

27

#7 Signalling Unit Module

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

P

S

U

1

P

S

U

2

S

1

S

2

S

3

S

4

P

C/

P

C

TU

C

T

U

I

T

U

I

TU

C

P

C/

P

C

S

5

S

6

S

7

S

8

P

S

U

4

P

S

U

3

8/9/2019 C-DOT Arch

28/53

28

SS7 Signalling Unit Module (SUM)

Any one of the ATU or DTU in a BM can

be replaced by SUM frame to support CCS7

signalling. Only one such unit is equippedin the exchange irrespective of its

configuration or capacity.

8/9/2019 C-DOT Arch

29/53

8/9/2019 C-DOT Arch

30/53

30

ISDN - Terminal Unit (ISTU)

One of the four ATUs/DTUs in a BM can be replaced by

ISTU to provide BRI/PRI interfaces in C-DOT DSS. The

only constraint is that ISTU has to be principal TU i.e.

directly connected to TSU on 8 Mbps PCM link. The ATU/DTU cannot be used in concentration with ISTU.

By equipping one ISTU in the exchange, a max. of 256 B

channels are available to the administrator which can be

configured as BRI, PRI or any mix as per site requirement.

Depending on the requirement of number of ISDN-Interfaces,

one or more ISTUs can be integrated in C-DOT DSS, either

in one BM or distributed across different BMs.

8/9/2019 C-DOT Arch

31/53

31

Time Switch Unit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

P

SU

II

T

G

A

M

F

C

M

F

C

S

CI

C

A

F

B

M

S

D

M

S

C

T

S

I

T

S

M

T

S

C

T

S

S

T

S

S

T

S

C

T

S

M

T

S

I

M

S

C

M

S

D

A

F

B

S

CI

C

M

F

C

M

F

C

T

G

A

P

SU

II

8/9/2019 C-DOT Arch

32/53

32

Time Switch Unit (TSU)

Time Switch Unit (TSU) implements threebasic functions as time switching within the

Base Module, routing of control-messageswithin the Base Module and across BaseModules and support services likeMF/DTMF circuits, answering circuits,

tones, etc. These functions are performed bythree different functional units, integrated astime switch unit in a single frame

8/9/2019 C-DOT Arch

33/53

33

8/9/2019 C-DOT Arch

34/53

34

Service Unit (SU)

Service Unit is integrated around three different cards asTone Generator with Answering Circuit (TGA), ServiceCircuit Interface Controller (SCIC). and MF/DTMFController (MFC) Card. MF/DTMF circuits(senders/receivers) are implemented by using single-chip,

4-channel Digital SignalP

rocessors (DSP

s). Two MFCcards are grouped to form a terminal group. Up to fourMFC Cards can be equipped.

The TGA and two groups of MFCs, form three terminalgroups towards the Service Circuits Interface (SCI).Service Circuit Interface multiplexes these three TGs

together with another terminal group from the BaseMessage Switch (BMS) to form a 128-channel, 8Mbps linkunder the control of Service Circuits Interface Controller(SCIC) and sends it towards the Time Switch.

8/9/2019 C-DOT Arch

35/53

35

Base Message Switch (BMS)

Base Message Switch (BMS) routes the control messages

within the Base Module, across different Base Modules, andalso Administrative Module via the Central Module. It isimplemented around two different cards as Message SwitchController (MSC) with six direct HDLC-links and theMessage Switch Device (MSD) Card implementing 16

switched HDLC links. As a unit, total 22 HDLC channels are implemented for

communication with the Base Processor, Time SwitchController, Service Circuits Interface Controller, TerminalInterface Controller within the BM and the four CMS

complexes in CM. It acts as a message transfer point betweenthe Base Processor and these controllers. It receives messagesfrom the Base Processor and transmits them towards theappropriate controllers.

8/9/2019 C-DOT Arch

36/53

36

Time Switch (TS)

The Time Switch complex is implemented using three differentfunctional cards as multiplexer/de-multiplexer (TSM), timeswitch (TSS) and time switch controller (TSC). The TimeSwitch complex receives the following PCM links and performstime- switching on them for switching within the Base Module :

(a) Four 128-channel multiplexed links from four differentTerminal Units which may be any combination of. ATU, DTU,#7SU and ISTU.

(b) One 128-channel multiplexed BUS from the ServiceCircuits Interface Controller (SCIC) in the Time Switch Unit.

(c) Three 128-channel links to support onboard three partyconference circuits (3 x 128).

It multiplexes above 128-channel links to form a dual 512-channel, 4 Mbps multiplexed bus towards the Central Module.The individual buses are called Bus0 and Bus1. Besides this, italso provides network switched path for messagecommunication between Base Modules, between Base Moduleand Administrative Module, and between Base Module and

Central Module.

8/9/2019 C-DOT Arch

37/53

37

Base Processor Unit

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

P

S

U

II

P

C/

P

C

PC

/

PC

P

S

U

II

8/9/2019 C-DOT Arch

38/53

38

Base Processor Unit (BPU)

Base Processor Unit (BPU) is the master controller in the Base

Module. It is implemented as a duplicated controller withmemory units. These duplicated sub-units are realised in theform of the following cards :

Base Processor Controller (BPC) Card

Base Memory Extender (BME) Card

BPC controls time-switching within the Base Module via theBase Message Switch and the Time Switch Controller. Itcommunicates with the Administrative Processor via BaseMessage Switch for operations and maintenance functions. In aSBM configuration, BPC directly interfaces with the Alarm

Display Panel and the Input Output Module. To support 8,00,000 BHCA, the BPC card is replaced by High

performance Processor Card (HPC). It is pin to pin compatiblefor hardware and also for software so that they areinterchangeable jat any site to meet specific traffic requirement.

8/9/2019 C-DOT Arch

39/53

39

8/9/2019 C-DOT Arch

40/53

40

CENTRAL MODULE (CM)

Central Module (CM) is responsible for space switching of

inter-Base Module calls, communication between Base Modulesand the Administrative Module, clock distribution and networksynchronization.

For these functions, Central Module has a Space Switch, SpaceSwitch Controller and a Central Message Switch. CM providesconnectivity to 16 BMs if it is CM-L and 32 BMs if it is CM-XL.

Each BM interfaces with CM via two 512-channel parallel busesas BUS-0 and BUS-1, each operating at 4 Mbps.

These buses carry voice information of 512 terminations of theBase Module towards CM. In the reverse direction, after spaceswitching has been done in the Space Switch under the controlof Space Switch Controller (SSC), the same buses carry the

switched voice information for 512 terminations towards BM.Thus, in a 32 Base Module configuration, there are 64 parallel

buses carrying the voice information from Base Modules to theCentral Module, and also the switched information in thereverse direction.

8/9/2019 C-DOT Arch

41/53

41

8/9/2019 C-DOT Arch

42/53

42

CM-XL can be divided into four functional sub-blocks.1. BTU Bus Termination Unit which is the BM-CM

interface.

2. SSU Space Switch unit which performs the space

switching.

3. SCU Space switch control unit which controls the

BTU, SSU and the CMS (Central message switch) unit,

which handles the message links between BM and CM.

4. APU/HPU: Administrative Processing Unit/High

powerProcess Unit which interfaces with the IOP and

performs the administrative processes.

Building Blocks of CM

8/9/2019 C-DOT Arch

43/53

43

Space Switch (SS) and Space Switch Controller (SSC)

In order to take care of the large number of interface

signals, the switch portion of CM is divided into threestages viz. MUX stage, Switch stage and DEMUX stage.The MUX and DEMUX stages are implemented on singlecard to provide the Base Module to Central Moduleinterface in each direction. Interfacing and switching arecontrolled by SSC which provides control signals for the

MUX/DEMUX cards and the Space Switch Switch cards.Interconnection between MUX/DEMUX cards and theSpace Switch is shown in Figure 3.4.

MUX/DEMUX Cards extract the information from time-slots 0 and 1 of Bus0 and Bus1 from the Base Modules.These time-slots carry control message from each BaseModule and these messages are sent to the CentralMessage Switch (CMS). The CMS sends these messagesto the Space Switch Controller (SSC) on a 128 kbps link tocontrol space switching based upon this information.

8/9/2019 C-DOT Arch

44/53

44

8/9/2019 C-DOT Arch

45/53

45

Four 512-channel buses from four BMs aremultiplexed to form a 2048- channel, 16

Mbps multiplexed BUS which is sent to

both copies of the Space Switch SwitchCard. Space switching of these 2048

channels is done based upon the switching

information received by Space Switch

Controller (SSC) from CMS.

8/9/2019 C-DOT Arch

46/53

46

8/9/2019 C-DOT Arch

47/53

47

Clock Distribution

CM provides the central clock for distribution to the BaseModules. The 8 MHz clock may be locally generated atthe Central Clock (CCK) card in case of CM-XL and ofSpace Switch Clock (SCK) card in case of CM-L by usinghigh stability VCXO crystal or may be derived from an

external reference clock using the NetworkSynchronization Controller (NSC) card in case of CM-XLand Network Synchronization Equipment (NSE) in caseCM-L under the control of SSC.

In the event of failure of external reference or duplex

failure of the NSC cards/NSE, the local clock is fed in theholdover mode, synchronized to last reference value. Inany arrangement, the local or external clock is distributedvia Central Bus Extender (CBX) cards in case of CM-XL.

8/9/2019 C-DOT Arch

48/53

48

CLOCK DISTRIBUTION contnd

The CBX card provides an interface between SSC

and SSU. SSC makes any switch card access

through CBX. CBX also handles any power

supply errors in SSU and BTU. Each CCK-CBX-NSC complex form a security block i.e. CBX0

cannot be used with CCK1. Thus there is a copy 0

complex and a copy 1 complex. The CBX also

synchronizes all SSC accesses to SSU with the 16MHz clock as well as BTU.

8/9/2019 C-DOT Arch

49/53

49

Central Message Switch (CMS)

Central Message Switch (CMS) complex is

the central message transfer point of theswitch. It is implemented as four different

message switches, working in load-sharing

mode. Each message switch is a highperformance message routing block,

implemented by using high speed 32 bit

microprocessor MC 68040 in case of CM-

XL and 16 bit microprocessor MC 68000 in

case of CM L.

8/9/2019 C-DOT Arch

50/53

50

This card supports 38 HDLC links in case of CM-XL

with flexibility of programming individual HDLC links

up to 750 kbps. All Central Message Switches

(CMS1,2,3&4) are used for routing of messages across

the Base Modules. On the other hand only CMS1 and

CMS2 interface with the Administrative Module forrouting control message between Base Processors and

Administrative Processor. This communication is used

to access office data for routing inter- module calls and

administration and maintenance functions.

8/9/2019 C-DOT Arch

51/53

51

ADMINISTRATIVE MODULE (AM)

Administrative Module (AM) consists of a duplicated16/32-bit controller called the Administrative Processor(APC). It communicates with Base Processors via theCentral Message Switch for control messages and with the

duplicated Input Output Processors in the Input OutputModule for interfacing peripheral devices Administrative

processor is responsible for global routing, translation,resource allocation and all other functions that are

provided centrally in C-DOT DSS MAX. The

implementation of AM is similar to BaseP

rocessorComplex of BM, using the same hardware configuration.As explained earlier, HPC instead of BPC is used tosupport 8,00,000 BHCA.

8/9/2019 C-DOT Arch

52/53

52

INPUT OUTPUT MODULE (IOM)

Input Output Module (IOM) consists of duplicated InputOutput Processor (IOP). The Input Output Processor (IOP)is a general purpose computer with UNIX OperatingSystem. It is used as the front end processor in C-DOTDSS. It handles all the input and output functions in C-DOT DSS. The IOP is connected to AP/BP via HDLClinks. During normal operation, two IOPs interconnected

by a HDLC link, operate in a duplex configuration.Working as front end processor, it provides initial code

down load to the subsystems, man machine interface anddata storage for billing and other administrativeinformation. Refer Fig. 3.7 for IOP connectivity in thesystem and IOP-VH architecture.

8/9/2019 C-DOT Arch

53/53

53