Fluke 9100A Series, Manual

Page: 22 / 122

9100A-017
3-4
TRISTATE CONTROL 3.8.
A low signal on the TRISTATE input line of the Vector Output
I/O Module asynchronously tri-states the 40-pin output of the
module. The output of the module remains tri-stated after the
removal of the TRISTATE low signal until a
writeword or
writepin command has been executed or further vector driving
has occurred.
If the TRISTATE occurred during vector driving, the proper re-
covery time (txsu) must be met to have the next vector driven
out upon receipt of a clock (see Figure 3-2 and Table 2-1 in
Section 2 of this manual). If the recovery time is not met, the
output of the module remains tri-stated and the current vector is
effectively skipped. To prevent vectors from being skipped,
connect the external ENABLE line to the TRISTATE pin and
use the
enableoutput mode “high”.
Figure 3-2. TRISTATE Input Timing Diagram
One method of using the external tri-state feature would be when
the Vector Output I/O Module is connected to a peripheral port
on a bus of a UUT. The peripheral select line could be con-
nected to the TRISTATE input of the module. When the port is
not in use, the peripheral select line would tri-state the module.