National Instruments SCXI-1121 User Manual
Page 102
Chapter 5
Programming
© National Instruments Corporation
5-11
Single-Module Multiplexed Scanning (Direct)
To perform simple channel scanning, you must cable the SCXI-1121 to a
data acquisition board. See Chapter 2,
Configuration and Installation
, for
more information.
To program the module for scanned channel measurements, write the
binary pattern
10ScXXXCC XX001101
to the SCXI-1121 Configuration
Register. CC represents the starting channel number.
Single-Module Multiplexed Scanning (Indirect)
To indirectly scan a module, send the output of the scanned module onto
Analog Bus 0, where it will be picked up by another module and
transmitted to the data acquisition board.
Channel Scanning from Other Modules
To scan measurements from other modules, you must cable the SCXI-1121
to a data acquisition board. See Chapter 2,
Configuration and Installation
,
for more information. The module programming steps are as follows:
1.
Perform any necessary programming to ensure that no modules are
driving Analog Bus 0. For an SCXI-1121, clearing AB0EN in the
Configuration Register will ensure that its output is not driving AB0.
2.
Write the binary pattern
10XXXXXX XX100011
to the SCXI-1121
Configuration Register. This step disables the SCXI-1121 from driving
Analog Bus 0 and allows Analog Bus 0 to drive MCH0 through the
output buffer.
3.
Program the other module to be scanned.
Channel Scanning from the SCXI-1121 via Another Module
To scan the SCXI-1121 via other modules, you must cable the other
module to a data acquisition board and the other module must be able to
transfer Analog Bus 0 to the data acquisition board. The other module must
also be able to send a SCANCLK*-compatible signal on TRIG0. See
Chapter 2,
Configuration and Installation
, for more information. The
module programming steps are as follows:
1.
Perform any necessary programming to ensure that no modules are
driving Analog Bus 0. For an SCXI-1121, clearing AB0EN in the
Configuration Register will ensure that its output is not driving AB0.