Phytec eGrabber-4plus, Hardware Manual

Page: 176 / 206

eGrabber-4plus
166 
PHYTEC Meßtechnik GmbH 2004 L-608e_4
•
During full image digitalization first a half image appeared or the
digitalization has not yet begun, since a leading second half image
(even) is still expected.
•
The interrupt was possibly generated by another device on the
PCI-Bus, which is mapped on the same interrupt channel.
Therefore in the event that an interrupt occurs it is always necessary to
test, by means of a query to Data_Present, what the cause of the
interrupt was and whether this event was the one expected.
.
The interrupt function therefore represents an expansion of the
Data_Present function, which minimizes unnecessary Data_Present
queries. However, it doesn’t replace the Data_Present function.
Note:
Be aware that interrupts are constantly being generated as soon as a
video signal is connected to the preset video input. The interrupts
occur in 20 ms intervals. Unusually strong interference in the input
signal as well as switching input channels can also generate an
interrupt.
The interrupt function should only be switched on during an active
digitalization procedure, in other words in the space between
Start_Grabber and Stop_Grabber.
The eGrabber-4plus generates the first interrupt INTA in its
PCI-socket. Depending on the socket where it is located as well as the
arrangement of interrupts resulting form the BIOS, this hardware
interrupt is assigned an IRQ-number. This IRQ-number can be queried
via the operating system.
Caution:
First arrange an interrupt routine that can handle the IRQ generated by
the Grabber. Only then should you generate the interrupt.
In order to reset the interrupt flags in the Grabber after an interrupt has
occurred, the function Reset_Interrupt must be called up in the
interrupt routine.