System for transferring data between I/O devices and main or expanded storage under dynamic control of independent indirect address words (IDAWs)
First Claim
1. A method of enabling an I/O device under control of a channel program to directly transfer data to/from any of a plurality of electronic storage media in a data processing system, comprising the steps ofexecuting the channel program by an I/O subsystem of the data processing system, the channel program including channel control words (CCWs), including CCWs specifying a read or write operation and containing an IDAW (indirect data address word) control bit for indicating whether an address in the CCW points to an IDAW list containing one or more IDAWs,accessing the IDAW list addressed by a current CCW in the channel program,detecting a current IDAW beginning with a first IDAW in the IDAW list, including detecting a state of a storage selection control field (V) in the current IDAW to identify one of the electronic storage media under control of the current IDAW, and an address contained in the current IDAW for addressing a location in the identified electronic storage media,dynamically controlling switching between different electronic storage media by providing an electronic storage identification in each IDAW in the IDAW list to control media switching independently of the electronic storage identification in any other IDAW in the IDAW list, andtransferring the data between the I/O device and the location in the electronic storage medium identified in the current IDAW.
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Accused Products
Abstract
Enables an I/O channel program to use IDAWs (indirect data address words) to control data transfers from/to an I/O (input/output) device to/from either or both of ES (expanded storage) and/or system MS (main storage), in which data moved to/from ES does not move through MS. ES and MS are plural electronic storage media in a data processing system, and the I/O device is any I/O device selectable by the system. Intermixing of data transfers between ES and MS may be controlled by a single IDAW list accessed by a channel control word (CCW) in a channel program in a data transfer direction indicated in the CCW without any channel mode change.
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Citations
18 Claims
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1. A method of enabling an I/O device under control of a channel program to directly transfer data to/from any of a plurality of electronic storage media in a data processing system, comprising the steps of
executing the channel program by an I/O subsystem of the data processing system, the channel program including channel control words (CCWs), including CCWs specifying a read or write operation and containing an IDAW (indirect data address word) control bit for indicating whether an address in the CCW points to an IDAW list containing one or more IDAWs, accessing the IDAW list addressed by a current CCW in the channel program, detecting a current IDAW beginning with a first IDAW in the IDAW list, including detecting a state of a storage selection control field (V) in the current IDAW to identify one of the electronic storage media under control of the current IDAW, and an address contained in the current IDAW for addressing a location in the identified electronic storage media, dynamically controlling switching between different electronic storage media by providing an electronic storage identification in each IDAW in the IDAW list to control media switching independently of the electronic storage identification in any other IDAW in the IDAW list, and transferring the data between the I/O device and the location in the electronic storage medium identified in the current IDAW.
Specification