ADLINK Technology NuDAQ cPCI-7249R, User Manual, Page: 45 / 74

Operation Theory 31
72XX Series
User’s Manual
4.3 Interrupt Multiplexing
4.3.1 Architecture
The 7248/96 series products have a powerful and flexible interrupt
multiplexing circuit which is suitable for many applications. The
board is capable of accepting
Dual Interrupts . The dual interrupt
means that the hardware can generate two interrupt request sig-
nals at the same time and the software can service these two
request signals by ISR. Note that the dual interrupts do not imply
the card occupies two IRQ levels.
The two interrupt request signals (INT1 and INT2) come from digi-
tal input signals or the timer/counter output. An interrupt source
multiplexer (MUX) is used to select the IRQ sources. Fig 4.3
shows the interrupt system.
4.3.2 IRQ Level Setting
There is only one IRQ level requested by this card, although it is a
dual interrupt system. The motherboard circuits will transfer INTA#
to one of the PC IRQ levels. The IRQ level is set by the PCI Plug
and Play BIOS and saved in the PCI controller. Users can obtain
the IRQ level setting in software library.
Figure 4-3: Dual Interrupt System of PCI-7224/7248/96
Note: * This interrupt is not available in PCI-7224
PCI
Controller
INTA#
IRQ
Flip-
Flops
INT1
INT2
Clear IRQ
INT1
MUX
P1C0
~P1C0 & P1C3
Event Counter
INT2
MUX
P2C0 (*)
~P2C0 & P2C3 (*)
Timer IRQ