AMD-K6 Datasheet, PDF (208/346 Pages) Advanced Micro Devices – AMD-K6 Processor

AMD-K6^® Processor Data Sheet
Preliminary Information
20695H/0—March 1998
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 71 illustrates an implementation of external logic for
supporting floating-point exceptions. The following example
explains the operation of the external logic in Figure 71:
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 96 and “IGNNE#
(Ignore Numeric Exception)” on page 100 for more details.
AMD-K6^®
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 71. External Logic for Supporting Floating-Point Exceptions
190
Floating-Point and Multimedia Execution Units
Chapter 9