AMD AMD-K6-2/500AFX Data Sheet - Page 228
Floating-Point and Multimedia Execution Units, AMD-K6, 2 Processor Data Sheet,
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AMD-K6®-2 Processor Data Sheet Preliminary Information 21850J/0-February 2000 instruction. IGNNE# is used by the external hardware to control the effect of an unmasked floating-point exception. Under certain circumstances, if IGNNE# is sampled asserted, the processor ignores the floating-point exception. Figure 84 illustrates an implementation of external logic for supporting floating-point exceptions. The following example explains the operation of the external logic in Figure 84: As the result of a floating-point exception, the processor asserts FERR#. The assertion of FERR# and the sampling of IGNNE# negated indicates the processor has stopped instruction execution and is waiting for an interrupt. The assertion of FERR# leads to the assertion of INTR by the interrupt controller. The processor acknowledges the interrupt and jumps to the corresponding interrupt service routine in which an I/O write cycle to address port F0h leads to the assertion of IGNNE#. When IGNNE# is sampled asserted, the processor ignores the floating-point exception and continues instruction execution. When the processor negates FERR#, the external logic negates IGNNE#. See "FERR# (Floating-Point Error)" on page 102 and "IGNNE# (Ignore Numeric Exception)" on page 106 for more details. AMD-K6®-2 Processor FERR# I/O Address Port F0h RESET "1" INTR IGNNE# IGNNE# Flip-Flop CLOCK Q DATA Q CLEAR FERR# Flip-Flop CLOCK Q DATA Q CLEAR Interrupt Controller IRQ13 Figure 84. External Logic for Supporting Floating-Point Exceptions 208 Floating-Point and Multimedia Execution Units Chapter 9