Patent GB-1407139-A (GB)
Title: Stored programme-controlled data exchange systems
IPC: H04L12/52
Filed: 1973-04-12
Abstract: 1407139 Data exchanges SIEMENS AG 12 April 1973 [31 May 1972] 17751/73 Heading H4P In a stored programme-controlled data exchange system, comprising a central store unit containing data and programmes for operation of the system, and a plurality of processing units which cyclically co-operate with said central unit, at least one of which operates as a programme control unit, and at least one as a line termination unit, to which are connected a plurality of transmission lines bearing dialling signals corresponding to dialled characters, conversion of the dialling signals into dialled characters is effected centrally within the system in a character handling unit, common to the transmission lines, containing a peripheral section which controls traffic with the central store, a control section which controls operations to be executed within said character handling unit, and a channel store acting as a special storage section. The channel store is divided into individual channel storage zones, each containing a series of cells which, at the beginning of a character handling process initiated by the programme control unit are allocated individually to the connection lines for the duration of a character handling process, the connection line to which they are allocated being determined by the storage of the number of the line. The character unit handles reception of commands and data in the channel store and, for transfer of reports and data from the channel store, obtains access, in cyclic fashion, to specific zones in the central store provided for the accommodation of commands, reports and data. The arrangement is stated to reduce the internal load relative to previous systems where to effect analysis of dialled characters it is necessary to convert received signals representative of dialled characters into parallel characters and reversely for transmission. The total of all channel cells and hence a plurality of conversion possibilities may be controlled by a single section. The optional allocation of channel cells with co-operation of the character handling unit reduces the necessary capacity of the channel store to that determined by estimated traffic load i.e. diversity can be applied. As a result of optional allocation, it is possible to make allocation in accordance with telegraphic speed or code of subscriber's lines. Where constricted in modular form, in the event of breakdown of the character handling unit, the programme unit can assume its functions hence redundant duplication is avoided enabling the system to continue at reduced level of activity. Advantageously across connection is provided between the character handling and line termination units via which control signals and information can be exchanged thus enabling a reduced capacity central store. Polarity charge reports resulting in transmission of polarity charges via the connection line can be transferred directly via the cross connection to the line termination unit. Since series/parallel and paralled series conversion takes place frequently the elimination of additional storage cycles provides economy. Character handling unit ZE contains a peripheral section NA, control section USt and channel store KAS, and co-operates with central store SP via input/output unit SAES through line termination unit LE and programme control PE, also NA controls traffic between character handling unit ZE including control section USt and central store SP. Via cross connection QV, section NA also has direct access to LE enabling it to effect read out of polarity changes by polarity change commands, also effect transmission of polarity changes by transfer of polarity change reports in cyclic manner. In USt character conversion ser/parallel/ser. are controlled, which involves selecting a particular cell, then processing the content. Directly addressable channel store KAS has individual storage zones B1 subdivided and preferably assigned selectively to lines of different speeds according to a variable programme. Before commencement of conversion a free channel is seized: allocation can be controlled by PE or selected by ZE, the line number being recorded in a channel cell also a feeder cell, the former being re-allocated to another line at the end of conversion. Activity of ZE is initiated by PE which records a command for character conversion in zone BB in SP, the command also specifying whether character or block, parallel or series conversion. An application bit AB placed by PE in a part of SP (not shown) is evaluated by ZE. If allocation is effected by PE, the command word includes the channel number of a free channel cell. For transfer of command into NA, BB is read by NA, cell by cell, the block start being permanently wired in NA which contains a counter forming the address following. After transfer into a specific cell a character processing command in ZE is conveyed via NA to MB. The AB bit then causes processing of any outstanding information in PE which prevents it being overwritten before it has been acted upon. Normal cyclic processing may be interrupted while this is done. At the same time, ZE receives or emits characters from zone TB. Operation is described in greater detail with respect to Figs. 3-9 (not shown).