Channel control system having device control block and corresponding device control word with channel command part and I/O command part
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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Abstract
A device control word including a channel command part and an I/O command part is prepared in a main storage unit, and sent to a channel unit together. The channel command part has a common format for different types of I/O devices or I/O controllers thereof, while the I/O command part may have a different format for each type of the I/O devices. Thereby, the same channel unit can be used for or connected to different kinds of I/O controllers by simply modifying software in a central processing unit to correspond to respective I/O controllers.
118 Citations
6 Claims
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1. A data processing system, comprising:
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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, including at 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. - View Dependent Claims (2, 3)
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4. A channel control system for a data processing system including a main storage unit and at least one I/O controller connected to at least one I/O device, for decoding I/O commands used to directly control the I/O device, the main storage unit storing at least one device control word at least one and a device control block, including a device control word address, a channel status and a remaining byte count, the I/O controller generating a data transfer request for the main storage in dependence upon the I/O command part of the device control word corresponding thereto, said channel control system comprising:
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at least one device control register, operatively connected to said main storage unit, for receiving and storing the device control word address and the device control word from said main storage unit and for storing updates to the channel status of the device control block having the device control word address. means, operatively connected to the device control register, for transferring the I/O command part of the device control word to the I/O controller; means, operatively connected to the device control register, for preparing, concurrently with decoding of the I/O command part by the I/O controller, a data transfer between said channel control system and the main storage unit in dependence upon the channel command part of the device control word; and means for performing the data transfer between said channel control system and the main storage unit in dependence upon the data transfer request from the I/O controller, for initiating a request sense command automatically when the I/O command part produces an error status, for generating the channel status from sense information obtained in response to the request sense command and for transferring from the device control register to the main storage unit, the updates of the status to the device control block having the device control word address.
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5. A method for controlling a channel unit in a data processing system including a main storage unit and at least one I/O controller connected to at least one I/O device for decoding I/O commands used to directly control the I/O device, the main storage unit storing at least one device control word and at least one device control block, each the device control block having a corresponding I/O controller, a device control word address, a channel status and a remaining byte count, said method comprising the steps of:
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(a) storing, in the channel unit, the device control word address and the device control word from the main storage unit, the remaining byte count and updates to the channel status of the device control block having the device control block address, the device control word including a channel command part and an I/O command part; (b) transferring the I/O command part of the device control word to the I/O controller; (c) preparing, concurrently with decoding of the I/O command part by the I/O controller, a data transfer between the channel unit and the main storage unit in dependence upon the channel command part of the device control word; (d) performing the data transfer between the channel unit and the main storage unit in response to a data transfer request from the I/O controller; (e) initiating a request sense command automatically when the I/O part produces an error status; (f) generating the updatas to the channel status from sense information obtained in response to the request sense command; and (g) storing in the device control block having the device control word address in the main storage unit, the remaining byte count and the updates to the channel status updated in step (f). - View Dependent Claims (6)
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Specification