Specifications

Appendix B PC Bus Controllers 99
Setting the Interrupt Request
The pins labeled I2 – I15 on JP1 define the interrupt request (IRQ) for
the PC Bus touchscreen controller.
Valid IRQs are 2, 3, 4, 5, 10, 11, 12, and 15. Refer to Table 19.
The default is IRQ4.
You can use any IRQ for the PC Bus controller as long as another
device in your system configuration is not using the same IRQ. The
PC Bus controller cannot share an IRQ with another device.
Predefined IRQs
As outlined in Table 19, some IRQs have predefined uses. For
example, most PC configurations use IRQs as follows:
Use IRQ2 for the second Programmable Interrupt Controller (PIC)
Use IRQ3 for either COM2 or COM4
Use IRQ4 for either COM1 or COM3
Use IRQ5 for the second parallel port (LPT2)
Additionally, some PC configurations may be using IRQ10 – IRQ15
for a modem or a primary/secondary IDE controller (for example, a
hard disk controller). You must know the resources that your system
devices use.
Preventing Device Conflicts
By default, the PC Bus controller uses COM3/IRQ4. If your system is
already using COM1/IRQ4 for an existing device, be sure to change
the IRQ that the PC Bus controller will use. The PC Bus controller
must use a unique IRQ and cannot share an IRQ with another device.
For example, a mouse typically uses COM1/IRQ4. If you are using a
mouse with the touchscreen, the mouse and the controller cannot both
use IRQ4. If both devices use the same IRQ, a hardware conflict will
result. The mouse or the touchscreen will not work.