AMD AMD-K6-2/500AFX Data Sheet - Page 151
Pipeline Data, Transition
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21850J/0-February 2000 Preliminary Information AMD-K6®-2 Processor Data Sheet Pipeline Data Transition sampled asserted). If the last BRDY# is not sampled asserted, the processor enters the Pipeline Data state. If the processor samples the last BRDY# asserted in this state, it determines if a bus transition is required between the current bus cycle and the pipelined bus cycle. A bus transition is required when the data bus direction changes between bus cycles, such as a memory write cycle followed by a memory read cycle. If a bus transition is required, the processor enters the Transition state for one clock to prevent data bus contention. If a bus transition is not required, the processor enters the Data state. The processor does not transition to the Data-NA# Requested state from the Pipeline Address state because the processor does not begin sampling NA# until it has exited the Pipeline Address state. Two bus cycles are concurrently executing in this state. The processor cannot issue any additional bus cycles until the current bus cycle is completed. The processor drives the data bus during write cycles or expects data to be returned during read cycles for the current bus cycle until the last BRDY# of the current bus cycle is sampled asserted. If the processor samples the last BRDY# asserted in this state, it determines if a bus transition is required between the current bus cycle and the pipelined bus cycle. If the bus transition is required, the processor enters the Transition state for one clock to prevent data bus contention. If a bus transition is not required, the processor enters the Data state (NA# was not sampled asserted) or the Data-NA# Requested state (NA# was sampled asserted). The processor enters this state for one clock during data bus transitions and enters the Data state on the next clock edge if NA# is not sampled asserted. The sole purpose of this state is to avoid bus contention caused by bus transitions during pipeline operation. Chapter 5 Bus Cycles 131