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Chapter 5
Programming
Note
If this module is an SCXI-1121 and is not going to be scanned (it is just being used
as an interface), write a zero to bit 2 (SCANCONEN) in the Configuration Register. The
start channel bits become don't care bits.
SCXI-1121 User Manual
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. Refer to
Chapter 2,
Configuration and
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.
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
Configuration Register, where CC 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 also be able to send a
SCANCLK*-compatible signal on TRIG0. Refer to 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.
Program the module that is connected to the data acquisition board to
connect Analog Bus 0 to the data acquisition board but not drive
Analog Bus 0 unless it is receiving an active low signal on SCANCON.
Also program the module to send a SCANCLK*-compatible signal
onto TRIG0. If this module is an SCXI-1121, this programming is
accomplished by writing the binary pattern
its Configuration Register.
3.
Program the other modules to be used in the scan to connect their
outputs to Analog Bus 0 but not to drive Analog Bus 0 unless receiving
an active low signal on SCANCON. Also program the other modules
Installation, for more information. The
01S
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5-12
to the SCXI-1121
10S
XXXCC XX001111
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ni.com
to
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