3. STD Bus Interface
26
In an edge-triggered architecture, multiple interrupt sources should not share the same
interrupt request signal because it is possible to miss an interrupt request from one
source while an interrupt request from another source is being serviced. For this
architecture, each interrupt source requires a unique connection to the interrupt
controller, as shown in the "
STD Bus Vectored Interrupt Structure
" figure following.
ZT 8904
STD BUS
INTRQ*
INTRQ*
INTRQ1*
INTRQ2*
INTRQ*
INTRQ*
INTRQ1*
INTRQ2*
INTERRUPT
SOURCE 7
INTERRUPT
SOURCE 3
INTERRUPT
SOURCE 2
INTERRUPT
SOURCE 1
INTERRUPT
SOURCE 4
STD Bus Vectored Interrupt Structure
Non-Maskable Interrupts
The ZT 8904 supports three sources of non-maskable interrupt requests. Each interrupt
source must be jumper enabled as described in the W9-11 jumper description in
Appendix A, "
Jumper Configurations
."
•
STD bus NMIRQ* (P46)
•
AC power-fail detection
•
Watchdog timer stage one