DM5210 analog input module 1-4 RTD Embedded Technologies, Inc.
Fig. 1-2a:
Factory Setting
Fig. 1-2b: Interrupt Source
Connected to IRQ3
Fig. 1-2 — Interrupt Channel Jumper, P3
P3 — Interrupt Channel Select (Factory Setting: Interrupt Channels Disabled; G Connected)
This header connector, shown in Figure 1-2, lets you connect any one of the three interrupt sources on P7 to an
interrupt channel, IRQ2 (highest priority channel) through IRQ7 (lowest priority channel). IRQ2 is the righttmost
channel and IRQ7 is the leftmost channel (next to last pair of pins). To activate a channel, you must install a jumper
vertically across the desired IRQ channel’s pair of pins. Figure 1-2a shows the factory setting; Figure 1-2b shows the
interrupt source connected to IRQ3.
This module supports an interrupt sharing mode where the pins labeled G, connect a 1 kilohm pull-down resistor
to the output of a high-impedance tri-state driver which carries the interrupt request signal. This pull-down resistor
pulls the interrupt request line low whenever interrupts are not active. Whenever an interrupt request is made, the tri-
state buffer is enabled, forcing the output high and generating an interrupt. You can monitor the interrupt status
through bit 1 in the status word (I/O address location BA + 10). After the interrupt has been serviced, the reset
command returns the IRQ line low, disabling the tri-state buffer, and pulling the output low again. Figure 1-3 shows
this circuit. Because the interrupt request line is pulled low only by the pull-down resistor, you can have two or more
modules which share the same IRQ channel. You can tell which module issued the interrupt request by monitoring
each module’s IRQ status bit. If you are not planning on sharing interrupts or if you are not sure that your CPU
supports interrupt sharing, it is best to disable this feature and use the interrupts in the normal mode. This will insure
compatibility with all CPUs. See chapter 4 for details on disabling the interrupt sharing circuit.
NOTE: When you use multiple modules that share the same interrupt, only one module should have the G
jumper installed. The rest should be disconnected. Whenever you operate a single module, the G jumper should be
installed. Whenever you operate the module with interrupt sharing disabled, the G jumper should be removed.
Fig. 1-3 — Pulling Down the Interrupt Request Line
2
3
4
5
6
7
G
2
3
4
5
6
7
G
P3
P3
IRQ
IRQ
INTERRUPT
+5 V
INTERRUPT
REGISTER
EXT INT
CLR
IRQ STATUS
P3
G
CLR
CLK
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