16.2 R4400 Master/Checker Mode

Fault History

Two internal fault history bits, Output Fault History and Input Fault History, record output faults and certain input faults reported through the Fault* pin. These bits are cleared with each deassertion of Reset*.

The two fault history bits are readable when Reset* is asserted, and the Fault* pin changes from reporting live faults to indicating which fault history bit was set when Reset* was deasserted in the previous cycle. The ModeIn pin acts as selector; if ModeIn = 0, Fault* indicates the inverted state of the Output fault history bit. If ModeIn = 1, Fault* indicates the inverted state of the Input fault history bit.

The fault history bits can be reset (cleared) while the R4400 processor is running by asserting 1 to the ModeIn pin. Consequently, ModeIn must be held to 0 to maintain the status of the fault history bits. Table 16-6 presents this information in tabular form.

Table 16-6 R4400 Fault History Bit Encoding

Copyright 1996, MIPS Technologies, Inc. -- 21 MAR 96

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