HP 61010A Owner's Manual page 29

choice of 16 start bits. If you specify a length of 16 bits,
you only have a choice of one start bit (bit 0). This
prevents the previously specified length of the data
segment from being truncated.
The following illustration shows you which input bits are
read when a length of 4 and a start bit of 8 is specified.
This example shows how the length corresponds to the
number of bits to the left of and including the start bit.
Note that the start bit cannot be a number greater than 12,
otherwise the length of the data field would be truncated.
Unspecified input bits will not be read.
X X X X I X X X X | XXXXXXXX
bit 15 - bit 0
THRESHOLD ■ is a voltage level that defines the crossover
point or dividing line between two logic states. The default
threshold voltage level is 1.36 V. How the Digital Input
interprets the logic states depends upon the setting of the
logic sense.
When the logic sense is positive, voltages above the
threshold level will be interpreted as a logic "high";
voltages below the threshold level will be interpreted as a
logic "low". When the logic sense is negative, voltages
above the threshold level will be interpreted as a logic
"low"; voltages below the threshold level will be
interpreted as a logic "high".
To change the threshold, point to and select the threshold
voltage field. There are two ways you can change the
threshold. You can select the .New Value softkey from the
keyboard and enter a new value, or you can modify the
existing value by using the keyboard softkeys that
correspond with the ones shown on your screen: Both
methods are explained in Chapter 4 of the System
Owner's Manual. Valid entries are voltages in the range of
-10.24 V to +10,16 V with a resolution of 0.08 V.
Manual Instrument Control 3*5