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9-6
Digital outputs
The digital I/O port has five digital outputs. Each digital output can be used as a sink to
control devices (e.g., relays) or as a source to provide input to external logic (TTL or
CMOS) circuitry. The simplified schematic for the digital outputs are shown in
Note that this illustration shows the schematic for one digital output. All five digital output
circuits are identical.
Figure 9-3
Digital I/O port simplified schematic
Control
Line
The five digital output lines (pins 1 through 5) are controlled by limit operations. Each of
these five outputs correspond to the following limit operations:
Digital Output 1 - Low Limit 1 (LO1)
Digital Output 2 - High Limit 1 (HI1)
Digital Output 3 - Low Limit 2 (LO2)
Digital Output 4 - High Limit 2 (HI2)
Digital Output 5 - Master Limit (logical OR of the four above limits)
When a limit (LO1, HI1, LO2, HI2) is reached, the digital output line for that limit will be
pulled high or low. When a reading is within the limit, the output line is released. Digital
output 5 is the logical OR of the four limits. Therefore, if any of the four limits are reached
or exceeded, output 5 will be pulled high or low.
Model 2790
+5V
33V
Digital Output
Flyback Diode
®
2790 SourceMeter
Switch System Reference Manual
Pin 7 (+5V to +33V)
4.75kΩ
(Pull-up)
Digital Output
Pin 9 - Digital Ground
Figure
9-3.
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