Ziatech Corporation ZT 8809A, Руководство по эксплуатации

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Numeric Data Processor (8087)
Use the lowest priority interrupt input to the interrupt controller for
the 8087, which is IR7 at the PIC. This requires wire-wrapping the
8087 INT to IR7.
Refer to Chapter 12 for further information
regarding the interrupt controller. The 8087 interrupt handler should
allow further interrupts by higher priority events. The interrupt
controller’s priority system automatically prevents the 8087 from
disturbing other interrupts without adding extra code to those other
interrupt routines.
Multiple 8087 interrupts
The previous case holds, except interrupt handlers may also generate
numeric interrupts. Connect the 8087 INT signal to multiple interrupt
inputs. One input would still be the lowest priority input, as in case 4.
Interrupt handlers that may generate a numeric interrupt require
another 8087 INT connection to the next highest priority interrupt.
Normally the higher priority numeric interrupt inputs would be
masked and the low priority numeric interrupt enabled. The higher
priority interrupt input would be unmasked only when servicing an
interrupt that requires 8087 exception handling.
Note: For the physical interrupt configuration for your system, refer
to the section on jumper configurations in Appendix A and to the
discussion of the interrupt controller in Chapter 12.
For more
information on the 8087 exception handling, refer to the 8087
Numerics Supplement by Intel.
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