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IV. INTERRUPT LEVEL (IRQ)
The QS/ES-100M allows the use of any interrupt level in the range
IRQ2 to IRQ7, IRQ10 to IRQ12, IRQ14, or IRQ15, selected using jumper
pack J10. (Early versions of the QS/ES-100M are limited to IRQ2-7.) In
Figure 6, the factory default setting of IRQ3 is shown. To select a different
IRQ, move the jumper to the appropriate position on J10.
Figure 6 --- Interrupt level (IRQ) selection
Interrupt Sharing
All ports on the QS/ES-100M share the same interrupt level. In
addition, an interrupt sharing circuit allows the QS/ES-100M 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 QS/ES-100M 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 QS/ES-100M will be unable to
signal any further interrupts.
Interrupt Status Register
The QS/ES-100M 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 a 7. Virtually
no commercially available software makes use of the scratchpad register.
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
22
12
J10
Default is IRQ 3
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Quatech QS-100M/ES-100M User's Manual