10. Clock Interface
10.6 Processor Status Outputs
The R4400 processor provides eight status outputs, Status(7:0), aligned with each rising edge of MasterClock. At time T (the first PCycle of MasterClock when status is examined) these status outputs indicate whether the machine was running or stalled during the previous T-2 and T-3 PCycles, as follows:
- If the machine was stalled during the T-2 or T-3 PCycles, the status outputs indicate the type of stall which occurred (listed in Table 10-1).
- If the machine was running during the T-2 or T-3 PCycles, the status outputs describe the type of instruction which occupied the WriteBack pipeline stage during the T-2 or T-3 PCycles, and which was successfully completed (listed in Table 10-1).
- The status outputs also indicate if an instruction in the T-2 or
T-3 PCycle was killed, and if so, states the cause (listed in Table 10-1.
The Status(7:0) bits are treated as two fields, as follows:
- The Status(7:4) field indicates the internal status of the processor during PCycle T-3.
- The Status(3:0) bits indicate the internal status of the processor during the PCycle T-2.
Table 10-1 shows the encoding of processor's status for pins Status(7:4) or Status(3:0).
Table 10-1 Encoding of R4400 Processor Internal State by Status(7:4) or Status(3:0)
Copyright 1996, MIPS Technologies, Inc. -- 21 MAR 96
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