ADLINK PCI-7258 - Manual (Page 30)

22 • Operation Theory
4.2 Isolated Digital Input
The PCI-7258 contains 2 opto-isolated digital input channels. The circuit
diagram of the isolated input channel is shown below.
Figure 8: Photo-Coupler
The digital input is routed through a photo-coupler (PC3H4), so that the
connections are not polarity sensitive whether using positive or negative
voltages. The PCI-7258 digital input has an inline 2.4kΩ resistor and the
input voltage can ranges from 0 to 24V.
4.3 Interrupt Architecture
PCI-7258 has a powerful dual interrupt routing scheme and the interrupt
sources are on the digital input channels 0 and 1. Using these interrupts will
make handling complicated digital information much easier and relief your
computer from the heavy burden of dealing with digital input data. Note that
dual interrupts does not mean the card occupies two IRQ levels. The
interrupt will occur only when digital input level changes from 0 to 1. In other
words, the interrupt condition occurs on the rising edge, triggered on the DI
channel. Be sure to clear the interrupt request after handling the ISR or the
next interrupt request will not be received normally. For more information
about the interrupt operation, refer to section 5.6.
DIGND
DI
2.4 KΩ