User`s manual

. INTERRUPT LEVEL (IRQ)
The ES-100D allows the use of any interrupt level in the range IRQ2 to IRQ7,
IRQ10 to IRQ12, IRQ14, or IRQ15, selected using jumper pack J2. In Figure 6, the
factory default setting of IRQ3 is shown. To select a different IRQ, move the jumper to
the appropriate position on J2.
1 2 3 4 5 6 7 8 9 10 11
IRQ7 IRQ2 IRQ3 IRQ4 IRQ5 IRQ6
IRQ11 IRQ12 IRQ14 IRQ15 IRQ10
13
14
15 16 17 18 19 20 21 2212
Default is IRQ 3
---
J2
Figure --- Interrupt level (IRQ) selection
Interrupt Sharing
All ports on the ES-100D share the same interrupt level. In addition, an
interrupt sharing circuit allows the ES-100D to share its interrupt with another Quatech
adapter supporting sharable interrupts. In either case, the software driving the serial
ports must determine which port or ports are requesting service when an interrupt is
generated.
The ES-100D signals a hardware interrupt when any port requires service. The
interrupt signal is maintained until no port requires service. Because the ISA bus is
edge-sensitive, this behavior forces the interrupt service routine to ensure that all ports
are checked before exiting. A way to do this is to poll each port until an interrupting
port is found. After servicing the port, all ports should be checked again. If any
interrupting port is left unserviced the ES-100D will be unable to signal any further
interrupts.
Interrupt Status register
The ES-100D is equipped with an interrupt status register which can be used to
simplify the servicing of shared interrupts. If this feature is enabled, the read-only
interrupt status register is accessed in place of the scratchpad of any given UART at
base address + 7. Virtually no commercially available software makes use of the
scratchpad register. The choice of using the interrupt status register or the UART
scratchpads is made using position 6 of switch SW2 as shown in Figure 7.
6 Quatech ES-100D User's Manual