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always indicates which Logic sense is currently active. The
output control signals are unaffected by this field.
For example, assume that you are going to enter a decimal
value of 100 in the output value field. If the length of the
data segment is 16 with a start bit of 0, a positive logic
sense would set output bits 2, 5, and 6 high and all other
bits low. A negative logic sense would set output bits 2, 5,
and 6 low and all other bits high.
OUTPUT VALUE * consists of an entry field that lets you
enter a value that determines the settings of the output
bits. As previously discussed, the settings of the base,
length, start, and logic sense fields will determine the
values that you can enter into the output value field. To
enter the output value, simply point to and select the
output value field. Use the keyboard keys to position the
cursor, type in the new value, and press iRelurnl . Note
that the output bits are not set to the new value unless the
output field indicates ENABLED.
DRIVER - lets you specify either an open collector output,
or a TTL logic level output, When you point to and select
this field, it toggles between TTL and OPEN COLLECT.
The field always indicates which output type is currently
active. Specifications for both output types are in Table
1
-
1
.
To prevent damage to the instrument, disable the output
whenever you change the driver.
An open collector output is used when output signals
above 5 V are required, or when the output is used to
power a device such as a LED or relay coil. An external
power supply is required to drive the open collector
outputs, Depending on your application, an external pull-
up resistor or protection diode may also be required.
Manual Instrument Control
3-13
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