Chapter 5
Programming
© National Instruments Corporation
5-9
SCXI-1120 User Manual
Single-Module Multiplexed Scanning (Direct)
To perform simple channel scanning, you must cable the SCXI-1120 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
10XXXCCC
XX001101
to the SCXI-1120 Configuration Register.
CCC
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
is 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-1120 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-1120, 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-1120 Configuration Register.
This step disables the SCXI-1120 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-1120 via Another Module. To scan the SCXI-1120 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-1120, clearing AB0EN in the Configuration Register will ensure that its output
is not driving AB0.
2. Program the other module not to drive Analog Bus 0, but to send Analog Bus 0 to the data
acquisition board. Also program the other module to send a SCANCLK*-compatible signal
to TRIG0.
3. Write the binary pattern
01XXXCCC XX001111
to the SCXI-1120 Configuration Register,
where
CCC
is the starting channel number.
Multiple-Module Multiplexed Scanning
To scan multiple modules, you must connect one module to the data acquisition board, and the
module must be able to transfer Analog Bus 0 to the data acquisition board. This module must
