| 摘要 |
1,108,806. Communication systems. INTERNATIONAL BUSINESS MACHINES CORPORATION. 5 April, 1965 [I Sept., 1964 (2)], No. 14260/65. Heading G4A. A communication system for linking a computer with input/output devices (e.g. punched card, magnetic tape, real time devices) comprises a first and a plurality of second information handling terminals, the first terminal (associated with the computer) including means for providing addresses, commands and data to out lines connected to the second terminals, each second terminal (associated with input/output devices) including means for providing addresses, status information and data to a plurality of in lines connected to the first terminal, and the out and in lines having at least one associated tag line energizable to indicate the nature of the information currently being provided to the associated lines. The particular embodiment is similar to those of Specifications 1,108,804 and 1,108,805 which are referred to, but the description is more detailed regarding mode of operation and Figs. 4A-4K (not shown) provide detailed flow drawings of the mode of operation. Delays are provided during (parallel) information transfer for deskewing purposes. The first terminal selects a second terminal by providing its address. If no second terminal recognises this address as its own, an error indication is given (Fig. 4D, not shown). All input/output devices are reset when both an " operational out " line (otherwise used for interlocking purposes) and a " suppress out " line are down. If " suppress out " is up when " operational out " drops, only the input/output device in operation on the system resets. Presentation of status information to the first terminal is prevented if the " suppress out " line is up, as is data transfer involving non-cyclic input/output devices, i.e. those that can wait for transfer without overrun (e.g. buffered devices). The " supress out " line is also used for indicating " command chaining," i.e. a succession of operations initiated by the first terminal at the same second terminal. Input/output devices may be time-divisionmultiplexed on to the lines communicating with the first terminal, each device allowing another device to acquire the lines after dealing with one unit of data only (" multiplex mode "), or alternatively an input/output device may deal with a block of data before losing the use of the lines (" burst mode "). |
