Patent GB-1446610-A (GB)
Title: Digital control processor
IPC: G05B19/05
Filed: 1973-11-13
Abstract: 1446610 Digital control processor L M ERICSSON PTY Ltd 13 Nov 1973 52731/73 Heading G4A [Also in Division H4] A processor for controlling the states of a plurality of external devices includes a memory storing words each containing information concerning the state of an associated external device, the words being arranged to be read out in order and used in combination with the actual state of the associated device to determine the operation to be performed. Thus instead of the usual two-cycle operation of obtaining an instruction and subsequently operating on data, the instruction address is derived at least in part from a data word which is accessed first. As described a control processor acts as an interface and supervisory processor between a digital PABX described in Specification 1,446,609 and six incoming/outgoing junctors 13 leading to a conventional system, but it is also stated that it could be used as an interface for a processor used to control industrial processes. As shown, 12 bit words are fed in parallel into a store 10 and appear subsequently in the same order at the output. Each word is normally processed and re-written in store 10 but may cause itself to be erased. Each word includes a 3-bit address which via a selector 14 selects one of six junctor relay sets 13, or via line 26 and interface 12 where it combines with four bits of an instruction from a line 30 is transmitted to the PABX processor. Information from the PABX processor or the relay sets is encoded at 15 and together with four call state bits specifying for example "idle" "incoming call" &c. and a four-bit count field on path 24 from store 10, access a location of a read only memory 16 to obtain an instruction two bits of which are decoded at 20 to determine the primary function to be performed, i.e. (a) to set a combination of relays in the relay set currently selected, (b) to signal the PABX processor, (c) to set the call state bits of the word from 10 used to access that instruction to a predetermined value or (d) to set the count field of that word to a given value. In each case of (a), (c) and (d) the value to which setting takes place is determined by four bits of the instruction on lines 25. The two remaining bits of the instruction are decoded at 17 and control the assembly at 19 of another word and its rewrite into store 10. One word in the store 10 called the "end word" stores in its first three bits a zero "junctor address". This junctor does not exist and is the address of the PABX processor. This word does not perform the usual functions but controls the writing into the store 10 of words in response to requests from the PABX processor. Thus a word may be constructed from a junction number, an action code and a digit for transmission, these being supplied by the PABX processor and corresponding to the junctor address, call state bits and count field respectively. Alternatively the PABX processor may cause the sequence state bits of the end word to be set to "idle", "incoming call" or any other state. The end word then initiates a search for a junctor in that state by decrementing its count field (this being effected at 18) once per cycle to generate the junctor addresses. Each junctor has an associated bistable which is reset by the end word and set by the first word in store 10 that contains the address of that junctor, other words in 10 containing that address being ineffective until the said first word has completed its function and caused itself to be erased.