| 摘要 |
A conditioned memory access apparatus and method for use in a data processing system comprising several processors which can concurrently accede to common resources provides that the actual access to a common resource be preceded by an occupation operation activated by a <<Test & Set>> command. Such operation consists in reading the information stored in a determined position of the common resource and in writing in the same determined common position a first information of resource occupation and a second information identifying the processor which wants to occupy the resource. The write operation is conditioned by the previous content of the determined position. If the first information, already contained into the determined position, indicates that the resource is already busy, the write operation will not take place and likewise the resource occupation will not take place too. The conditioning of the write operation is performed by control circuits (22, 24) in the memory unit, which circuits receive in input a signal decoded from the Test & Set Command, a write enable command generated by memory control unit (14) and the information stored in a determined position of the common resource. |
