DM5210 analog input module 4-12 RTD Embedded Technologies, Inc.
Interrupts
• What Is an Interrupt?
An interrupt is an event that causes the processor in your computer to temporarily halt its current process and
execute another routine. Upon completion of the new routine, control is returned to the original routine at the point
where its execution was interrupted.
Interrupts are very handy for dealing with asynchronous events (events that occur at less than regular intervals).
Keyboard activity is a good example; your computer cannot predict when you might press a key and it would be a
waste of processor time for it to do nothing while waiting for a keystroke to occur. Thus, the interrupt scheme is used
and the processor proceeds with other tasks. Then, when a keystroke does occur, the keyboard ‘interrupts’ the
processor, and the processor gets the keyboard data, places it in memory, and then returns to what it was doing
before it was interrupted. Other common devices that use interrupts are modems, disk drives, and mice.
Your 210/5210 can interrupt the processor when a variety of conditions are met. By using these interrupts, you
can write software that effectively deals with real world events.
• Interrupt Request Lines
To allow different peripheral devices to generate interrupts on the same computer, the PC bus has eight different
interrupt request (IRQ) lines. A transition from low to high on one of these lines generates an interrupt request which
is handled by the PC’s interrupt controller. The interrupt controller checks to see if interrupts are to be acknowledged
from that IRQ and, if another interrupt is already in progress, it decides if the new request should supersede the one
in progress or if it has to wait until the one in progress is done. This prioritizing allows an interrupt to be interrupted
8-Bit A/D Code Table
Input Voltage Range
Output Code
0 to +10 Volts
-10 to +10 Volts
-5 to +5 Volts
+9.9609 volts
+9.9219 volts
+4.9609 volts
MSB 1111 1111 LSB
+7.500 volts
+5.000 volts
+2.500 volts
1100 0000
+5.000 volts
0 volts
0 volts
1000 0000
+2.500 volts
-5.000 volts
-2.500 volts
0100 0000
0 volts
-10.000 volts
-5.000 volts
0000 0000
For 0 to +10 & ±5 volts, 1 LSB = 39.063 millivolts; for ±10 volts, 1 LSB = 78.126 millivolts.
12-Bit A/D Code Table
Input Voltage Range
Output Code
0 to +10 Volts
-10 to +10 Volts
-5 to +5 Volts
+9.9976 volts
+9.9951 volts
+4.9976 volts
MSB 1111 1111 1111 LSB
+7.500 volts
+5.000 volts
+2.500 volts
1100 0000 0000
+5.000 volts
0 volts
0 volts
1000 0000 0000
+2.500 volts
-5.000 volts
-2.500 volts
0100 0000 0000
0 volts
-10.000 volts
-5.000 volts
0000 0000 0000
For 0 to +10 & ±5 volts, 1 LSB = 2.44 millivolts; for ±10 volts, 1 LSB = 4.88 millivolts.
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