Chapter 2
Configuration and Installation
©
National Instruments Corporation
2-5
Using Jumpers W42 and W43
Leave jumpers W42 and W 43 in their factory-default settings if any one of
the following applies:
•
The SCXI-1120/D is not cabled to a DAQ device
•
The SCXI-1120/D is cabled to a DAQ device, and the SCXI chassis is
the only SCXI chassis cabled to that DAQ device
•
The SCXI-1120/D is cabled to a DAQ device, and there are multiple
SCXI chassis cabled to that DAQ device with shielded cables
In the factory-default setting, jumper W43 connects, after buffering, the
SCXIbus Master-In-Slave-Out (MISO) line to the SERDATOUT pin of the
rear signal connector. In this setting, along with the proper setting of
jumper W42, the DAQ device can read the SCXI-1120/D Module ID
Register. See Chapter 3,
, for the pin equivalencies of
the SCXI-1120/D rear signal connector and the DAQ device I/O connector.
Revisions A and B of the SCXI-1120
On Revision A and B SCXI-1120 modules, jumper W42 is not used. 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-1120 modules cabled to the DAQ device, you
can access the MISO line in only one chassis. Pick one of the chassis that
has the SCXI-1120 cabled to the DAQ device. Set jumper W43 on the
SCXI-1120 to position 1. On the SCXI-1120 modules that are in the other
chassis and cabled to the DAQ device, 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.
Revisions C and Later of the SCXI-1120 and All Revisions of
the SCXI-1120D
Jumper W42 in position 1 connects a 2.2 k
Ω
pullup resistor to the
SERDATOUT line. Position 3 does not connect the pullup resistor to
the SERDATOUT line.
The SERDATOUT line is driven with an open-collector driver.
(An open-collector driver drives low or goes to a high-impedance state,
relying on a pullup resistor to make the signal line go high.)
