Application programming interface for data transfer and bus management over a bus structure

摘要

An application programming interface implements and manages isochronous and asynchronous data transfer operations between an application and a bus structure. During an asynchronous transfer the API includes the ability to transfer any amount of data between one or more local data buffers within the application and a range of addresses over the bus structure using one or more asynchronous transactions. An automatic transaction generator may be used to automatically generate the transactions necessary to complete the data transfer. The API also includes the ability to transfer data between the application and another node on the bus structure isochronously over a dedicated channel. During an isochronous data transfer, a buffer management scheme is used to manage a linked list of data buffer descriptors. This linked descriptor list can form a circular list of buffers and include a forward pointer to the next buffer in the list and a backward pointer to the previous buffer in the list for each buffer. The linked descriptor list may all form a linear list to which the application can append additional buffers or remove existing buffers from the list. During isochronous transfers of data, the API provides implementation of a resynchronisation event in the stream of data allowing for resynchronisation by the application to a specific point within the data. Implementation is also provided for a callback routine for each buffer in the list which calls the application at a predetermined point during the transfer of data.