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.Each EM number has a one-to-one corre-spondence to one regional program and its data.Control module (CM) isname for a regional program controlling one EM.So, usually one CM controls one EM, see Figure 13.5.Exceptions includetime-switch modules (TSMs) where one CM supervises two EMs.RPCM 0 EM 0CM 1 EM 1CM n EM nFigure 13.5One CM controls one EM227Plex-C 2The design rule in reference [3] summarises EM and CM in this way.AnEM is" a magazine" an extension unit" an exclusion unit" a blocking unit,while a CM is" a regional software unit.The exchange technician may block and deblock EMs, like most otherhardware.The operating system can start and restart CMs, like most othersoftware units.To start a CM, insert a periodic signal in the job table.RP2 FunctionsThe RP2 controls most types of application hardware, excluding the sub-scriber switch and, in the future, the group switch.AXE exchanges haveup to 1,024 RP2s.Figure 13.6, a repeat of Figure 13.2, shows the connec-tions between the RP2 and its partners.ExtensionEM-0 EM-1 EM-15ModulesEMBRP RegionalRPProcessorsRPBCentral ProcessorCP-A CP-Bwith MaintenanceMAUUnit (MAU)CP = Central Processor MAU = Maintenance UnixEM = Extension Module RP = Regional ProcessorEMB = Extension Module Bus RPB = Regional processor busFigure 13.6The RP2 hardware structureEach EM has APT devices of one type, for example, 32 BT devices.Dif-ferent EMs may contain different device types.228CP-RP/EMRP InteractionRP2 SoftwareReceiving CP-RP signals has higher priority than scanning the hardwareunits.The operating system REX (regional executive program) adminis-ters the work of the RP2.REX determines which program is running.The RP2 execution splits into primary intervals of 5 ms.During this inter-val, the control module once scans all devices in the EM and processes allincoming CP-RP signals.These tasks usually take less time than 5 ms.Theremaining time in the primary interval is devoted to special maintenanceprograms, MRP, which perform a number of different tests on the RP.Figure 13.7 describes the RP operating mode during a primary interval.Ifno CP signal is received, the software scans the devices in the EMs only.The software scans the devices in the EMs in consecutive order beginningwith EM15 and ending with EM0.After scanning each EM, the operatingsystem, REX, takes over and determines which application program tostart next.CP-RP signalto CM6REX REX REX REX REX REX REX REX REX REXCM15 CM14 CM13 CM6 CM12 CM0 MRP CM15Time0 ms 5 msFigure 13.7RP2 job execution during a primary intervalFigure 13.7 shows a CP-RP signal arriving for CM/EM6 while scanningCM/EM13.The control system immediately interrupts the application pro-gram for CM/EM13, and a microprogram stores the CP-RP signal data inthe RP memory.Then, the RP software resumes scanning of CM/EM13.After the scanning of CM/EM13 has terminated, the operating system,REX, takes control as usual.REX starts the application program for theCP-RP signal.When this program finishes, REX calls the application pro-gram of the next CM/EM to be scanned, CM/EM12.If there is time left in the primary interval after scanning all CM/EMs,REX calls the MRP programs.MRP programs routinely test the RP.AsFigure 13.7 shows, MRP programs execute in short sequences.After eachsequence, the control returns to REX to see if there are any CP-RP signalsto process, or if the primary interval is over.If there are no waiting CP-RP229Plex-C 2signals, and there is still time left, MRP continues for a short sequence.After the primary interval, REX starts all over scanning CM/EM15.If the primary interval is over before all CM/EMs have been scanned, thenext interval does not start.The operating system delays the next primaryinterval until all CMs are complete.However, if the primary interval isexceeded several times in a row, the RP software notifies the CP software.EMRP FunctionsIn addition to its use in the subscriber switch subsystem (SSS), EMRPscontrol functions in a number of other AXE subsystems, such as input-out-put, ISDN and mobile telephony.However, this section concentrates on theEMRP in the SSS.As for RPs, the EMRPs control telephony hardware and execute ordersinitiated by CP-EMRP signals.A single or duplicated EMRP controls theequipment in a single EM, also known as line switch module (LSM) in anextension module group (EMG) which constitutes a subscriber stage.An LSM includes equipment for connecting up to 128 subscribers.AnEMG contains a maximum of 16 LSMs giving a total connection capacityof 2048 per EMG.The EMRP is mounted on the EM, that is LSM, it con-trols.There are up to 32 EMRPs in each LMG.See Figure 13.8 [ Pobierz całość w formacie PDF ]