HP 61010A Owner's Manual page 70

Input/Output
Data Transfer
Programmable
Input Threshold
After your Digital I/O passes these preliminary tests, it will
appear in a menu along with the other instruments in
your system. This menu is the starting point for the
instrument-specific verification tests for all of your
instruments. To continue testing your Digital I/O, you
must select it from this list and press the TEST softkey
(f7). (When you select an instrument from this list, the
ACTIVE indicator on the front of the instrument lights
up.) Specifically, the Digital I/O verification checks three
different functions of the instrument: input/output data
transfer, the programmable input threshold, and the
handshake control circuits.
This first test allows you to check each of the 16 output
and input bits of the instrument one at a time, Each
output bit is used to check the corresponding input bit
(i.e. output bit 0 checks input bit 0, etc). The computer's
screen displays the necessary test connections that you
must make. When you have connected the specified input
and output bits together with a clip lead, logic high and
then logic low are programmed to the Digital Output and
read by the Digital Input. If the proper values are read by
the Digital Input, the test passes.
If there is a problem with either an input or an output bit,
the test will fail.
The input threshold, which is actually a reference voltage,
is programmable for the Digital Input. To verify that this
function is operating correctly, you must connect any one
of the 16 input bits to any one of the 16 output bits. The
program sets all the output bits to logic low, then reads all
the input bits. The reference voltage is ramped from -IV
to +1 V to verify that the connected input bit reads a logic
high when the reference voltage is greater than the input
voltage (the logic low supplied by the output bit). Next,
the 16 output bits are programmed to a logic high and the
reference voltage is ramped, from 4 V to 5.5 V to see at
which voltage level the Digital Input properly reads a logic
low.
B-2 Verification Procedures