Chapter 12
298 MIPS R4000 Microprocessor User's Manual
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.
†
† When using the R4000SC processor, IvdAck* and IvdErr* must be connected to Vcc.
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