12.2 System Interface Description
Handshake Signals
The processor manages the flow of requests through the following eight control signals:
- RdRdy*, WrRdy* are used by the external agent to indicate when it can accept a new read (RdRdy*) or write (WrRdy*) transaction.
- ExtRqst*, Release* are used to transfer control of the SysAD and SysCmd buses. ExtRqst* is used by an external agent to indicate a need to control the interface. Release* is asserted by the processor when it transfers the mastership of the System interface to the external agent.
- The R4000 processor uses ValidOut* and the external agent uses ValidIn* to indicate valid command/data on the SysCmd/SysAD buses.
- IvdAck*, IvdErr* are used in multiprocessor systems; they are asserted by the external agent to indicate the successful completion (IvdAck*) or the unsuccessful completion (IvdErr*) of a pending processor invalidate or update request.*1
Copyright 1996, MIPS Technologies, Inc. -- 21 MAR 96
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