Change Of State Detection; What Is Cos; Structure Of Cos Detection & Dual Interrupt System; Cos Detection - NuDAQ PCI-7230 User Manual

4.3 Change of State Detection

4.3.1 What is COS?

The COS (Change of State) means when the input state (logic level) is
changed from low to high or from high to low. The COS detection circuit is used
to detect the edge of level change. In the PCI-7233 card, the COS detection
circuit is applied to all the 32 channels input channels. When anyone channel
is changed, the COS detection circuit generate an interrupt request signal.
4.3.2 Structure of COS detection & Dual Interrupt System
The dual interrupt system is used in PCI-7233. Dual interrupt means the
hardware can generate two interrupt request signals in the same time and the
software can service these two request with ISR. Note that the dual interrupt
do not mean the card occupy two IRQ levels. The two interrupt request signals
(INT1 and INT2) are comes from COS detection output signal #1 and #2. The
INT1 is inserted when any channel of 0 ~ 15 is changed. The INT2 is inserted
when any channel of 16 ~ 31 is changed. Fig3.6.1 show the interrupt system.
Figure.3.6.1 Dual Interrupt System of PCI-7233

4.3.3 COS Detection

The following timing is an example of the COS detection. Every DI signal's
edge change can be detected. All the DI channels edge will be 'OR' together
to generate the INT1 or INT2 IRQ signals.
If INT1 or INT2 irq Signals generate, the signal will be latch its state. The user
cam use the "_7233_CLR_IRQ" function to clear, INT1 or INT2 IRQ signal
state.
DI0~
DI15
DI0~
PLD1
DI31
3 2
Channel
C l e a r
Isolated
Input
I R Q
D I 1 6 ~
DI31
PLD2
INT1
P C I
Bridge
INT2
PCI Bus
Operation Theorem 25