Parallel transfer size calculation and annulment determination in transfer controller with hub and ports

摘要

The transfer controller with hub and ports employs a parallel size calculation/write annulment decision. A default burst size register (501) stores a default burst size for the port. An address register (512) stores a next data address and initially stores the data transfer start address. A transfer count register (509) stores a transfer count of remaining data to be transferred and initially stores the number of words of the data transfer. A transfer size register (520) stores a data transfer size and initially stores the default burst size. A first comparator (508) determines the least of the default burst size and the transfer count. A two's complement unit (502) forms a two's complement of a number of least significant bits of said address store in said address register corresponding to the default burst size. A second comparator (506) determines the least of the two's complement and the output of the first comparator. A third comparator (521) enables data transfer at the next data address of the data transfer size when the second comparator output equals the data transfer size and annuls data transfer otherwise. This technique facilitates the process of setting up complex transfers without risking brute force inefficient processor cycles. Annulment determination allows detection of cases when a set of data cannot be output immediately and the destination pipeline postpones execution of the write command. <IMAGE>