National Instruments SCXI-1120 - page 62

Chapter 3 Theory of Operation
© National Instruments Corporation 3-15 SCXI-1120 User Manual
except during changes from one Slot 0 scan list entry to the next, when SCANCON pulses high
to make the MUXCOUNTER reload its starting channel. Notice that although you are using
only a single module, you can put many entries with different counts in the Slot 0 FIFO, so that
some channels are read more often than others. You cannot change the start channel in the
module Configuration Register during a scan.
Cable
Assembly
Data Acquisition Board
Analog Input
Timing Output
TRIG0
SCANCON X
SCANCLK
MCH0
SLOT 0
Eight Isolated
Floating
Single-Ended
Inputs
SCXI-1000 or SCXI-1001 Chassis
SLOT X
SCXI-1120
Figure 3-8. Single-Module Multiplexed Scanning (Direct)
Single-Module Multiplexed Scanning (Indirect)
In this mode, the SCXI-1120 is not directly cabled to the data acquisition board. Instead, you
connect another module to the data acquisition board, and the analog output of the SCXI-1120 is
sent over Analog Bus 0, through the intermediate module, and then to the data acquisition board.
The SCXI-1120 receives its MUXCOUNTER clock from TRIG0, which is sent by the
intermediate module, as shown in Figure 3-9. Slot 0 operation is the same for direct connection
scanning.
Cable
Assembly
Data Acquisition Board
Analog Input
Timing Output
Other
Module
Analog Bus 0
SCANCON X TRIG0
SCANCLK
MCH0
SCXI-1000 or SCXI-1001 Chassis
SLOT X
SLOT 0 SCXI-1120
Figure 3-9. Single-Module Multiplexed Scanning (Indirect)
Multiple-Module Multiplexed Scanning
In this mode, all the modules tie into Analog Bus 0 and SCANCON enables the output of their
amplifiers. The module that is directly cabled to the data acquisition board sends SCANCLK