Interrupt Control. HP (Hewlett-Packard) NuDAQ PCI-9111HR, PCI-9111DG/HR

4.2 Interrupt Control

4.2.1 System Architecture

The PCI-9111‘s interrupt system is a powerful and flexible system which is suitable for A/D data acquisition and many applications. The system is a Dual Interrupt System. The dual interrupt means the hardware can generate two interrupt request signals in the same time and the software can service these two request signals by ISR. Note that the dual interrupt does not mean the card occupies two IRQ levels.

The two interrupt request signals (INT1 and INT2) come from digital input signals or the timer/counter output. An interrupt source multiplexer (MUX) is used to select the IRQ sources. Fig 4.2.1 shows the inte rrupt system.

INT #A

PCI

Controller

INT1

INT2

IRQ

Flip-

Flops

INT1

MUX

INT2

MUX

Clear IRQ

Figure 4.2.1 Dual Interrupt System of PCI-9111

AD EOC

FIFO

Half-full

Pacer

External

IRQ

4.2.2 IRQ Level Setting

There is only one IRQ level is used by this card, although it is a dual interrupt system. This card uses INT #A interrupt request signal to PCI bus. The motherboard circuits will transfer INT #A to one of the AT bus

IRQ levels. The IRQ level is set by the PCI plug and play BIOS and saved in the PCI controller. It is not necessary for users to set the IRQ level.

4.2.3 Dual Interrupt System

The PCI controller of PCI-9111 can receive two hardware IRQ sources.

However, a PCI controller can generate only one IRQ to PCI bus, the two

IRQ sources must be distinguished by ISR of the application software if the two IRQ are all used.

The application software can use the “_9111_Get_Irq_Status” function to distinguish which interrupt is inserted. After servicing an IRQ signal,

Operation Theorem • 31