ADLINK ACL-8454/12 - Manual (Page 45)

Signal Connections & Applications • 37
4.9 Double Interrupt System
One Internal plus one external interrupt sources
The ACL-8454 provides double interrupt sources which are very useful in
some application. For example, most of the application needs a watchdog
timer to monitor the system periodically, hence, an IRQ channel is used. In
addition, the emergency control may be necessary, hence, an additional
external IRQ channel is helpful to handle the situation. Therefore, double
interrupt level is necessary. The external interrupt source can be routed to
COUT12 if 8254 chip #4 is not installed.
/COUT6
Counter #6
8254 Chip #2
C
G
O
IRQ channel : Watchdog Interrupt
JP1
COUT12
JP2
IRQ channel : External Interrupt
JP3
COUT12
Ext.Clk
Figure 4.8 Example of double interrupt system
Two internal interrupt sources
For certain application, /COUT6 is used to generate gate control pulse for
measuring frequency and to generate interrupt too. This internal IRQ
channel is used to calculate frequency data. However, another internal
watchdog timer interrupt may be still necessary. Users can install 8254 chip
#4 to get one more pair of cascaded counters (#11, #12). The COUT12 can
be used as watchdog interrupt source. Therefore, two internal interrupt
sources are available.