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Channel control system having device control block and corresponding device control word with channel command part and I/O command part

  • US 5,031,091 A
  • Filed: 11/08/1989
  • Issued: 07/09/1991
  • Est. Priority Date: 07/31/1986
  • Status: Expired due to Fees
First Claim
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1. A data processing system, comprising:

  • a central processing unit;

    a main storage unit, operatively connected to said central processing unit, for storing at least one device control word and at least one device control block, each device control word including a channel command part having at least a channel command code, a data length and a data address, and an I/O command part having at least and I/O command code and a data length, and each device control block including a device control word address, a channel status and a remaining byte count;

    an I/O device;

    an I/O controller directly connected to said I/O device for controlling same, said I/O controller including means for decoding the I/O command part and for making a data transfer request according to the I/O command part; and

    a channel unit, operatively connected to said central processing unit, said main storage unit and said I/O controller, includingat least one device control register for holding, channel status bytes, an address of the at least one device control block and the device control word read out from said main storage unit;

    means for transferring the I/O command part of the device control word from said main storage to said I/O controller and updated channel status bytes in said device control register to the at least one device control block;

    means for preparing, simultaneously with the decoding by said I/O controller, a data transfer between said channel unit and said main storage unit according to the channel command part of the device control word and for updating the channel status bytes in said device control register; and

    means for carrying out the data transfer between said channel unit and said main storage unit in response to the data transfer request from said I/O controller.

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