Patent GB-1260090-A (GB)
Title: Data processing systems
Inventor: QUINN THOMAS MICHAEL
IPC: G06F13/18
Filed: 1970-10-21
Abstract: 1,260,090. Automatic exchange systems. WESTERN ELECTRIC CO. Inc. 21 Oct., 1970 [21 Oct., 1969], No. 49931/70. Heading H4K. In a telephone exchange the control system comprises a data processing arrangement in which a program controlled processor and a wired logic processor share the same temporary memory, priority of access to the temporary memory alternating between the program controlled and wired logic processors. In basic operation cycles, referred to as minor cycles, the program control has priority of access in the first portion of each cycle while the wired logic has priority of access in the latter portions. The wired logic performs a portion of the digit receiving, digit sending, line scanning and data sending tasks. By assigning to the wired logic repetitive high rate functions for which accuracy of timing is required, program real-time is conserved. Moreover, program interrupts for the purpose of supervising telephone system input/output functions occur no more frequently than at 25 msec intervals. The processing machine cycle is 3 Ásec. and instruction implementation can take 1 to 6 such cycles while access to the temporary memory and peripheral access circuit may take 4 cycles at most. Whenever wired logic has access to the temporary memory the program control is barred and may in consequence stand idle for periods up to 9 Ásec. If a particular class of wired logic work remains unfinished at the end of a minor cycle the priority given to wired logic in accessing the temporary memory is extended into the next minor cycle and the program control is barred for a further fixed period sufficient to clear the backlog. Under the classification of non-deferrable quota work the wired logic processes data sending on 32 channels. In each minor cycle of 1À251 msec, the wired logic addresses the temporary memory to obtain two sixteen bit words, one bit corresponding to one of the 32 channels, so that data is sent at 800 bits/sec. Each data message sent comprises 64 serial bits. Data sending may be employed for the purpose of effecting control of remote subordinate offices. The exchange network uses reed relays and the conditions of 6576 lines are ascertained by eight duplicated scanners employing ferrod sensors after the manner of the Bell System No. 1 ESS. Line scanning is undertaken by the wired logic whenever it is not engaged with quota work and during times when neither the program nor the wired logic requires the peripheral access circuit. Scanning halts whenever a service request is found, when all lines have been scanned, or when the program effects an interrupt. Requests for service are detected from an inspection every 100 msec. The temporary memory provides 128 originating registers each comprising 8 successive words of 16 bits each. The digit sequence is detected by the wired logic which stores the digits in an allotted register where the program control subsequently acts upon the information from evaluations made after the first, second, third and seventh digits. The signalling employed in the exchange may be 2 x 1 out-of 4 frequency code, 2 out-of 6 frequency code or dial pulse. Prior to allotment of a call signalling receiver to a validated call origination the program control determines the signalling type and enters a record of the type in the register. In the ease of a substation equipped with both 2 x 1 out-of 4 frequency sending and sending by dial pulses it is left to the wired logic to determine which type of signal is being received and a receiver capable of detecting either kind of signalling is placed in service for the connection. It is assumed that such a station will not send both types of signal at the same time. Digit reception and transmission can be carried out in respect of the same register at the same time. Outpulsing can be at 20 or 10 impulses/sec. and the register carries a mark placed by the program control which instructs the wired logic to send, digit by digit, accordingly.  If the work of servicing registers, this being classified as deferrable quota work, is not complete at the end of a minor cycle the work is taken up at the beginning of the next cycle and is pursued for a maximum period of 192 Ásec., it being the rule that the wired logic completes the quota work of each minor cycle within the majority of such cycles. If, 24 Ásec. before the end of a minor cycle, it is established that quota work of the wired logic remains to be done, the priority of the wired logic in its access to the temporary memory is extended into so-called force time so that the non-deferrable quota work at least may be completed. The program control is held off by blocking the command translator and, when the program control indicates that it has relinquished its normal priority of access to the temporary memory and the peripheral access circuit, the wired logic proceeds with its backlog. Normal call processing functions are performed in an interrupt hierarchy by the program with interrupts spaced at intervals of 25 msec. or multiples of 25 msec. Information which is gathered by the interrupt sequence is further processed at base level where a timed interrupt sequence is in force for the despatch of data. If the time spent executing base level functions is less than 100 msec. additional maintenance work is added to the work list. If more than 325 msec. has been employed at base level there is a presumption of fault and remedial action is taken. Whereas the wired logic detects substation service requests trunk circuit service requests are detected by the programmed processor. A request for service indicated by wired logic is passed to the programmed processor during a 25 msec. scan and the program puts it on the timing work list to test persistence. If verified by persistence the request is put into the origination hopper and a transient call register is associated with the call and given the call identity and a call progress code. All other transient call registers, these being in the temporary memory, are examined to see if an originating register has been allocated already and, if not, an appropriate digit receiver and an originating register are allotted. The temporary memory incorporates two-word terminal memory records for each trunk, service circuit or junctor, and these are associated with the allotted digit receiver which is labelled with the address of the associated transient register which in turn is labelled with the address of the allotted originating register. The functional units of the program controlled processor arc described with reference to Figs. 2 to 5, (not shown), while the units of the wired logic processor are described with reference to Figs. 6 to 9 (not shown). Originating register, transient register and terminal memory data interfaces in the temporary memory are described with reference to Figs. 15, 16, and 17 respectively, (not shown). Outpulsing and associated outgoing trunk circuits are described with reference to Figs. 21 and 22 (not shown).