ADLINK Technology NuDAQ ACL-8454, User Manual

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Installation
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21
2.12 DuaI Interrupt System
One Internal plus one external interrput sources
The ACL-8454 has two interrupt sources on board. That means
the two interrupt levels or two IRQ lines can be used by this board.
The block diagram of the interrupt system is shown in Figure 2.15.
The two IRQ channels can be set by jumper
JP1 and JP2
respectively. The high IRQ level is jumper wired to IRQ 10~15 and
the low IRQ level is jumper wired to IRQ 3~9. The source of the high
IRQ level comes from
/COUT6 which is the reversed output of
cascaded counters.
Two internal interrput 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 is
available.
The reversed
COUT6 interrupt is very useful because the /COUT6 is
also send to the gate control of counter #1 ~ #4 for frequency
measurement. While
/COUT6 is high, the frequency measurement
is counting. When /COUT6 goes low, the counting is ending and an
interrupt is generated from interrupt system so that the software can
sample and memorize the result of frequency measurement. In
watchdog application, using reversed
COUT6 has no problems
because the frequcncy of COUT6 and reversed COUT6 is the same.
The sources of the low IRQ level comes from internal (
COUT12 ) or
external ( ECLK10 ) source which are jumper selectable by JP3 . Note
the COUT12 is not reversed counter output. The default setting (ACL-
8454/6) of the higher and lower IRQ levels come from /COUT6 and
ECLK10 respectively.
Note: The IRQ channels must not conflict with other add-on cards
on your PC.