Patent GB-1305771-A (GB)
IPC: H04Q3/545
Filed: 1970-04-02
Abstract: 1305771 Digital data processors WESTERN ELECTRIC CO Inc 2 April 1970 [3 April 1969 21 Oct 1969] 15603/70 Heading G4A [Also in Division H4] A register sender system comprises a common store having a plurality storage locations which receive signal information for different destinations, a corresponding plurality of sending devices each arranged to transmit the associated signal information in serial form and to modify the association stored information in accordance with each signal element transmitted, and an independently operating control unit which monitors the stored signal informations and enables and disables each sending device in accordance with its stored information. As described a telephone exchange employs two processors sharing a common memory and common peripheral access circuitry. One processor is a wired programme processor which is capable of performing various routine tasks such as detecting individual dial pulses of a digit and adding each detected pulse to a stored total, while the other is a programme controlled processor which performs the main tasks associated with the control of the exchange and which supervises the operations of the wired logic processor, e.g. to detect interdigit pauses &c., and to set up that processor to receive a further digit or to perform another of its routine tasks. The routine tasks performed by the wired processor are reading from store data words and entering them in a data sender, servicing digit receivers and senders and associated originating registers during the reception or transmission of the pulses of a digit, and scanning subscriber lines and trunks for calling condition. These tasks although relatively simple require frequent actions at intervals determined by external conditions (e.g. by data sending and pulse rate employed) and thus the inclusion of a wired processor avoids the frequent interrupts in the stored programme processor that would otherwise be necessary. The stored programme processor normally has priority in the use of the common memory and common peripheral access circuitry. The wired processor must (a) complete the serving of the data sender before the end of each 1À251 millisecond cycle and (b) service a group of digit receivers and senders before or immediately after the end of a cycle (different groups being serviced in successive cycles). If 24 microseconds before the end of a cycle (a) is not completed due to being unable to gain access to the common memory a flp-flop is at set causing the wired processor to have priority of access to the memory and if (b) is not complete by the end of a cycle a flip-flop is set causing the wired processor to have priority of access to the common peripheral access circuitry. This ensures that these tasks can be completed in the required time limits.  Scanning lines and trunks, digit transmission. -The line and trunk scanners include ferrods connected such that any off-hook supervisory state can be regarded as a request for service, each ferrod associated with a line or trunk which is in a served or talking state being disconnected so as to give an on-hook indication. Scanning of lines or trunks by the wired programme processor commences when it has been fed the address of a line or trunk at which to commence the scan, the wired programme processor is not performing tasks (a) and (b) above and the stored programme processor is -not using the peripheral access circuit. When an off-hook condition is detected a flag is set by the wired programme processor requesting the attention of the stored programme processor. If this condition persists for two successive cycles the stored programme processor assigns an idle originating register in the common memory and assigns either a dial pulse receiver or a combined dial pulse/multi-frequency receiver to the call in accordance with the type of dial signals as given by the translator. A subscribers line may have either a dial pulse sender, a multifrequency sender or both. During digit reception the stored programme processor resets once every 125 milliseconds a flag marking controlled the wired programme processor. The latter sets the flag for each dial pulse and increments a stored count by one. When the stored programme processor finds the flag already reset, i.e. a 125 microsecond interval occurs without the reception of a dial pulse, an interdigit pause is recognized and the stored count cleared to an appropriate digit location ready for the next digit. Digit transmission is effected in a similar manner and may be effected simultaneously with reception. During transmission, a digit count is entered by the stored programme processor in a send location together with an indication of the transmission rate. The wired programme processor decrements the count by one for each pulse sent and brings up a flag to the stored programme processor when a predetermined count is reached. Data sending.-The data to be sent is in the form of 16 bit data words compiled in the common memory by the programme controlled processor. The data sender has 32 channels each channel relating to a different message. The wired processor reads out two successive words from the memory during each cycle into a register which assigns one bit to each channel. Each message is transmitted as 64 serial bits taken from different data words during successive cycles. The last bits of each message together form an end of message code. A receiver is also shown. Programme controlled processor.-Various details of the programme controlled processor (Figs. 2 to 5, not shown, positioned side by side left to right in that order) are given. The processor includes a function register in which is stored the function to be performed on data in two other registers, a masking register which indicates to which bits the function is to be applied, a results register and a masking register which controls the replacement of selected bits in one of said other registers by corresponding bits of the result. It also includes a register adapted to receive the contents of one or two registers and add and/or shift the result or contents. Errors.-If an error is detected an automatic interrupt is effected. The normal programme cycle of the programme controlled processor includes error detection routines and if spare time is available further routines are automatically undertaken.