National Instruments SCXI-1120 - Manual (Page 63)

Theory of Operation Chapter 3
SCXI-1120 User Manual 3-16 © National Instruments Corporation
onto TRIG0 for the other modules and Slot 0, as shown in Figure 3-10. The scan list in Slot 0 is
programmed with the sequence of modules and the number of samples per entry.
SCANCLK
MCH0
Cable Assembly
Data Acquisition Board
Analog Input T
iming
Output
SLOT A SLOT B
SLOT 0
SLOT X
TRIG0
SCANCON A
SCANCON B
SCANCON X
SCXI-1000 or SCXI-1001 Chassis
Analog Bus 0
SCXI Module SCXI Module SCXI Module
Figure 3-10. Multiple-Module Multiplexed Scanning
Multiple-Chassis Scanning
In this mode, you attach each SCXI-1001 chassis to a daisy chain of cable assemblies and
multichassis adapter boards, as shown in Figure 3-11. You program each chassis separately, and
each chassis occupies a dedicated channel of the data acquisition board. Within each chassis,
scanning operations act as if the other chassis are not being used, with one exception–you must
program the Slot 0 scan list in each chassis with dummy entries of Slot 13 to fill the samples
when the data acquisition board will be sampling another chassis or data acquisition board
channel. This will keep the chassis synchronized. Notice that you can only perform
multiple-chassis scanning with the SCXI-1001 chassis and MIO-16 data acquisition boards. See
Chapter 5, Programming, for more information on multiple-chassis scanning. See Appendix E,
SCXI-1120 Cabling, for more information on the necessary cable accessories for multichassis
scanning.
Multichassis
Adapter
Chassis 2 Chassis 1
Data Acquisition Board
Timing Output
Input Ch. 0
Input Ch. 1
Input Ch. N
Chassis N
Multichassis
Adapter
Cable
Assemblies
Cable
Assembly
Multichassis
Adapter
Cable
Assembly
Chassis 2 Chassis
Figure 3-11. Multiple-Chassis Scanning