Byte count handling in serial channel extender with buffering for data pre-fetch
First Claim
1. A data processing system having apparatus (22) for interconnecting a parallel bus (26, 27) of a control unit (18) and a serial link (14) of a channel, said apparatus comprising:
- means (47) for storing a byte count,a buffer memory (39), a parallel bus (27m) for data to be stored in the buffer memory and a parallel bus (36) for data fetched from the buffer memory,means (30b) connected between said parallel busses of said buffer and connected to said parallel bus of the control unit for handling data transfer operations on said parallel bus according to a predetermined protocol,means (28,
29) connected to said serial link for sending and receiving frames on the serial link, said sending and receiving means including means for converting between a serial format of incoming or outgoing frames on the serial link and a parallel format of the control unit parallel bus and the buffer memory,means interconnecting said buffer memory, said means for handling operations on said parallel bus, and said sending and receiving means and controlling data transfers between said means connected to said serial link and said means for handling operations on said parallel bus,the frame format including a data field and a command field, the command field holding a selected one of a plurality of binary codes signifying the contents of the data field, a first command code signifying a data field containing a byte count for a data transfer and a second command code signifying a data field containing data for controlling the subsequent transfer of data to or from the control unit in an interlocked mode or a non-interlocked mode, andmeans (37) in said interconnecting and controlling means for decoding the command field of an incoming frame on said serial link and means (41) for transferring a byte count data field in an incoming frame to said byte count storing means.
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Accused Products
Abstract
A channel subsystem with a conventional serial extender link that causes communications between a channel and a control unit to be delayed by the additional time to transmit a message in one direction and to transmit an acknowledgement in the other direction. The channel subsystem also has a buffer and associated components (called a channel outboard box) that are used for prefetching data from processor memory or from a peripheral device without waiting for the acknowledgment routines that are commonly used on both an interlocked data transfer and a non-interlocked transfer (called data streaming). A system of counters and other components and associated operations maintain the correct byte count that would otherwise be maintained in a system without the prefetch buffer and with only a short serial link. A system of count and status frames provides for sending byte count and other status information between the channel and the outboard box.
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Citations
9 Claims
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1. A data processing system having apparatus (22) for interconnecting a parallel bus (26, 27) of a control unit (18) and a serial link (14) of a channel, said apparatus comprising:
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means (47) for storing a byte count, a buffer memory (39), a parallel bus (27m) for data to be stored in the buffer memory and a parallel bus (36) for data fetched from the buffer memory, means (30b) connected between said parallel busses of said buffer and connected to said parallel bus of the control unit for handling data transfer operations on said parallel bus according to a predetermined protocol, means (28,
29) connected to said serial link for sending and receiving frames on the serial link, said sending and receiving means including means for converting between a serial format of incoming or outgoing frames on the serial link and a parallel format of the control unit parallel bus and the buffer memory,means interconnecting said buffer memory, said means for handling operations on said parallel bus, and said sending and receiving means and controlling data transfers between said means connected to said serial link and said means for handling operations on said parallel bus, the frame format including a data field and a command field, the command field holding a selected one of a plurality of binary codes signifying the contents of the data field, a first command code signifying a data field containing a byte count for a data transfer and a second command code signifying a data field containing data for controlling the subsequent transfer of data to or from the control unit in an interlocked mode or a non-interlocked mode, and means (37) in said interconnecting and controlling means for decoding the command field of an incoming frame on said serial link and means (41) for transferring a byte count data field in an incoming frame to said byte count storing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification