Configuration and Installation
Chapter 2
SCXI-1120 User Manual
2-6
© National Instruments Corporation
acquisition board, those different modules will have jumpers similar to W43 and W42 of the
SCXI-1120. Set those jumpers on the different modules using the same method described here
for the SCXI-1120.
On Revision A and B SCXI-1120s, jumper W42 is not used. You set jumper W43 as explained
in the cases above, except in the case of a multichassis ribbon cable system. In a multichassis
ribbon cable system with Revision A and B SCXI-1120s cabled to the data acquisition board,
you can access the MISO line in only one chassis. Pick one of the chassis that has the
SCXI-1120 cabled to the DAQ board. Set jumper W43 on the SCXI-1120 to position 1. On the
SCXI-1120s that are in the other chassis and cabled to the data acquisition board, set jumper
W43 to position 3. Notice that you will only be able to access digital information from the
chassis that has the SCXI-1120 with jumper W43 set to position 1.
On Revision C and later modules, the SERDATOUT line is driven with an open-collector driver
(a driver that actively drives low or goes to a high-impedance state, relying on a pullup resistor to
make the signal line go high). When using a single chassis, leave W42 and W43 in position 1,
the factory default, on the SCXI-1120 that is connected to the data acquisition board. In this
setting, the module drives MISO to SERDATOUT and connects the necessary pullup resistor to
the SERDATOUT line. When using multiple chassis, leave jumper W43 in position 1 on all of
the SCXI-1120s that are cabled to the data acquisition board. Only one of the SCXI-1120s that
are cabled to the data acquisition board should have jumper W42 in position 1. It does not matter
which of the SCXI-1120s that are cabled to the data acquisition board has the pullup connected.
All of the other SCXI-1120 modules that are cabled to the data acquisition board should have
jumper W42 in position 3. The reason for this is that if too many pullup resistors are attached to
the SERDATOUT line, the drivers cannot drive the line low. See Table 2-1 for the description
and configuration of the jumper settings.
Table 2-1. Digital Signal Connections, Jumper Settings
Jumper
Description
Configuration
W42
W42
W43
W43
Connects pullup to SERDATOUT
(Revision C and later) factory-
default setting.
Parking position (not connected on
Revision A and B)
Connects MISO to SERDATOUT
Factory-default setting.
Parking position
•
•
•
3
2
1
•
•
•
3
2
1
•
•
•
3
2
1
•
•
•
3
2
1
(continues)