2. The method of claim 1 , wherein: said transmit buffer is a first-in-first-out buffer; said operation of the data transfer engine comprises, based on said set up, processing a sequence of descriptors in the data transfer engine; and the processing of the sequence of descriptors comprises: processing a first descriptor operating the data transfer engine to input said read request word into the first-in-first-out transmit buffer; processing one or more subsequent descriptors operating the data transfer engine to input a number of additional words into the first-in-first-out transmit buffer behind the read request word, the number being at least sufficient to fill said first-in-first-out transmit buffer to an upper stall threshold and arranged so as to generate a stall until said response word has been returned from the slave device; and following said subsequent descriptors in the sequence and synchronized to release of said stall of the first-in-first-out transmit buffer, processing one or more control descriptors operating the data transfer engine to perform said disabling of the first-in-first-out receive buffer.
2. The method of claim 1 , wherein: said transmit buffer is a first-in-first-out buffer; said operation of the data transfer engine comprises, based on said set up, processing a sequence of descriptors in the data transfer engine; and the processing of the sequence of descriptors comprises: processing a first descriptor operating the data transfer engine to input said read request word into the first-in-first-out transmit buffer; processing one or more subsequent descriptors operating the data transfer engine to input a number of additional words into the first-in-first-out transmit buffer behind the read request word, the number being at least sufficient to fill said first-in-first-out transmit buffer to an upper stall threshold and arranged so as to generate a stall until said response word has been returned from the slave device; and following said subsequent descriptors in the sequence and synchronized to release of said stall of the first-in-first-out transmit buffer, processing one or more control descriptors operating the data transfer engine to perform said disabling of the first-in-first-out receive buffer. 6. The method of claim 2 , wherein said sequence comprises a series of linked descriptors, each operating the data transfer engine to process the next in the sequence, and said set-up by the processor comprises identifying only an initial descriptor in the sequence.