GB1470328A - Stored programme controlled telephone exchange - Google Patents

Abstract

1470328 Data processing systems TELEFONAKTIEBOLAGET L M ERICSSON 9 April 1974 [9 April 1973] 15742/74 Heading G4A [Also in Division H4] In a stored program controlled telephone exchange including a plurality of functional units some but not all of which directly control telecommunication devices (e.g. cross-bar selectors) and with each of which are associated both data and instruction words in associated data and program storage sections, a central processing unit addresses an input address decoder of the storage arrangement via one of a number of addressing devices individually associated with the functional units. The object of the invention is to allow the system to readily adapt to various arrangements of the peripheral devices and in particular to restrict consequential program modification to the addressing device associated with those functional units giving rise to the modification. In one arrangement as shown a common program store SPS and a common data store SDS are used. The number of the functional unit to be processed next is entered in a register BNR of a plurality of operations registers OPR in the CPU, and this number sets the switches of a selector device SD to the corresponding position. The state of the selected functional unit as stored in a register SR in that unit is compared in a state table ST with a code in a register AXR indicative of the operation to be performed. If a non- allowable combination is detected an alarm AA is triggered. If as is normal an allowable combination is detected the address in a register AR is decoded at SADEC to read out a selected instruction or data word, this address having been calculated by an arithmetic unit ARU and translation device TD from the selected functional unit number, a number in a register DIR identifying a particular device served by that unit and a characteristic of the particular data or instruction distribution involved and as given by an addressing device AD individual to that functional unit. The characteristic given by the addressing device AD is a jump address from a register JR selected by a jump number supplied by the central processor unit via a register JNR or a data group address and the length of a data word, these data characteristics being selected at CDR in accordance with a data (variable) number specified by the CPU in a register VNR. These addresses may be relative to a base address given by a register CAR. Various embodiments with more and less common equipment are described. The central processor may be duplicated. The telecommunication devices may include line supervision circuits, cross-bar switches and magnetic tape units.