US 6,298,403 B1Granted

Host adapter having a snapshot mechanism

AssigneeAdaptec, Inc.

InventorsSalil Suri, Taikhim Henry Tan

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Abstract

A circuit collects data from a number of locations in a system memory of a personal computer, and can refetch the collected data at any time, e.g. when an adapter for transferring data between a computer bus and a peripheral bus that includes the circuit encounter an unexpected event (such as an error) in the transmission (or retransmission) of data to a first peripheral device. So the adapter simply flushes the data on encountering the unexpected event. Thereafter, the adapter switches context, to transfer data to a second peripheral device. At a later time, the circuit in the adapter refetches the flushed data, for retransmission of the data to the first peripheral device. To refetch the flushed data, the circuit does not traverse backwards through a scatter/gather data transfer pointer list (described above) that is used to collect the data from system memory. Instead, the circuit initially stores the values (collectively called “snapshot”) of signals in various registers at the time of initial receipt of the data, and at a later time loads the saved snapshot to refetch data that was flushed.

Claims10

Dependent claims

An adapter for transferring data between a peripheral bus coupled to a peripheral device and a computer bus coupled to a system memory inside a personal computer, the adapter circuit comprising:

a data transfer module coupled to the peripheral bus;
and
a host interface module coupled to the computer bus, the host interface module being also coupled to the data transfer module for transfer of the data between the peripheral bus and the computer bus, the host interface module including:
an address register for holding an address signal indicative of a location in the system memory;
a count register for holding a count signal indicative of the amount of data to be transferred from the system memory;
a restart memory, to recover from an interrupt, connected to the address register and the count register, having a plurality of groups of storage elements, each group of storage elements including an address storage element and a count storage element;
wherein:
the host interface module stores a value of an address in the address register, and stores a value of a count in the count register when storing data from the location in system memory, the value in the address register and the value in the count register changing during receipt of data;
and
the host interface module copies the values from the address register into the address storage element of a selected one of the groups, and from the count register into the count storage element in the selected group always at the beginning of the transfer of data, the values being used to identify data to be transferred from a processor.

7 more elements

Dependencies are inferred from the claim text.