| 摘要 |
PURPOSE:To efficiently transfer data by reading and updating a pointer in a bus cycle which conducts buffer management. CONSTITUTION:In a system consisting of three units of CPU which constitute a multiprocessor, a common bus 4, and peripheral devices 5 such as a communi cation control device which carries out data transfer, two or more bus cycles are needed when a large amount of data is transferred from 1 to 5. If 2 transfers data to 5 in between a bus cycle and a bus cycle, the data from 1 and that from 2 will be mixed up in the buffer 5; therefore, such transfer must be prohibited. For this reason, in the case where data is to be transferred from 1 to 5, the pointer P, indicating the freeness of the transmission buffer, initially is read. At this time, p is updated to p+n (where, n is the size of the data which 1 is bout to transfer). 1 transfers the data to the position that p indicates. Where 2 transfers data to the same transfer buffer during 1 is transferring data, 2 reads p, obtaining p+n. In this case, p becomes p+n+m (where, m is the size of the data which 2 is about to transfer). |
