National Instruments NI SCXI-1336, Руководство пользователя

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Chapter 2 Using the SCXI-1129
SCXI-1129 User Manual 2-20 ni.com
the need to daisy-chain terminal blocks. You can also use the 4
× 16
matrix
in a similar fashion. You cannot accomplish this connection with other
matrix types since the row granularity is greater than four, or in the case of
the 4
× 64
matrix, you cannot subdivide it.
To make a larger matrix, such as a 16
× 64
matrix, you must make both
column and row expansions. To build a larger matrix, follow these steps:
1. Expand the columns to the target number, 64 in this case, by
connecting the rows of the appropriate number of SCXI-1335s
(8
× 32
matrix), two in this case, using matrix expansion cables.
This configuration results in a 8
× 64
matrix block.
2. Expand the rows to the target number, 16 in this case, by connecting
the columns of the appropriate number of 8
× 64
matrix blocks, two in
this case, using matrix expansion plugs.
Figure 2-13 shows four SCXI-1335s connected to form a 16
×
64 matrix.
Hardware and Software Scanning
The SCXI-1129 provides a very flexible scanning architecture. You have
individual control over every crosspoint and configuration relay, which
means you can:
• Do random switching
• Do multiplexing
• Use the 4
×
16 matrix banks independently
There are two basic methods of scanning: hardware-timed scanning
and software scanning. In hardware-timed scanning, the measurement
instrument, such as a DMM, communicates through digital triggering
signals to the SCXI-1129. In its simple form, hardware-timed scanning
uses one triggering signal to advance the matrix to the next state in the
scan. This process is called synchronous scanning.
Note When using a DMM to control a SCXI chassis, synchronous mode is the only mode
in which the DMM and the SCXI-1129 operate.
Another hardware-timed scanning method is called handshaking. While
synchronous scanning requires just one signal from the instrument to the
matrix, handshaking requires an additional signal connected from the
matrix to the instrument. This additional trigger, Scanner Advanced,
notifies the measuring instrument that the matrix has settled and that the
next measurement can be made. This method is useful when using