GB1478503A - Method and apparatus for exchanging information between a central unit and a peripheral controller in a data-processing installation - Google Patents

Abstract

1478503 Transmitting data COMPAGNIE INTERNATIONALE POUR L'INFORMATIQUE CII-HONEYWELL BULL 28 Nov 1974 [30 Nov 1973] 51651/74 Heading G4A In a transmission system between a stored program central processing unit and a peripheral controller, a signal STO (Fig. 11) is transmitted from the central unit together with data, the signal STO resulting in a signal STI from the peripheral controller to the central unit which causes STO to fall off, the peripheral controller then accepting the transmitted data. Similarly to transmit data from the peripheral to the central unit first signal STI is generated signal X 1 (Fig. 7a) becoming 1 so that the output X of store S 1 becomes 1. If the input/output controller is available the output gate A1 drops to zero to enable gate A2 to generate signal STO which in turn turns off signal STI (which enables gate A 1 to disable gate A 2 and so switch off signal STO). Timing signals TMO and TMI indicating that the peripheral and central units respectively have finished transferring data may be similarly generated. The exchange of information is controlled by a group of micro-instructions contained in a store associated with the peripheral controller, a service code accompanying the microinstructions indicating the nature of the exchange. Transfer of data cannot occur before an initializing service code sequence has occurred. This is transmitted to the peripheral controller in response to a signal CPW (Fig. 11) which generates the initializing signal SCI. After initialization the central unit transmits data, if the initialization is for data to be transferred or, if it is for a new channel program, a number of bytes the first corresponding to the number of the channel associated with the program and the remaining bytes corresponding to the channel program.