National Instruments NI SCXI-1336, Руководство пользователя

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Chapter 2 Using the SCXI-1129
SCXI-1129 User Manual 2-24 ni.com
For example, you can connect the VMC of the DMM to the SCXI-1129
through a spring terminal labeled EXTRIGIN on the SCXI-1333 terminal
block. You must also connect the SCANADVD signal from the SCXI-1333
terminal block to your DMM external trigger input. Refer to Figure 2-2.
If you have more than one module in your system, it is not necessary to
cable the VMC to each module. You can bus the VMC onto the SCXI
backplane (Trig 0 to Trig 7), allowing other modules to be triggered as
shown in Figure 2-15.
Multimodule Scanning
The SCXI-1129 supports three multimodule operation modes. This enables
you to control many SCXI-1129 modules as if they were a single unit.
Chain Triggering
Multimodule scanning on the SCXI-1129 is similar to single-module
scanning. When scanning multiple modules, there is a chance of channel
contention. In other words, more than one module could be competing for
the same channel if switches do not open and close at the right time. You
can avoid this problem if you have one module triggering the following
module after it has already switched and settled. Below is an example of
three SCXI-1129 modules being scanned. The measurement device is
receiving the SCANADVD signals as well as sending the VMC signals to
the switches.
Example
Module 1 Switches, sends SCANADVD, waits for VMC, sends
trigger to module 2, waits for trigger from module 3.
Module 2 Waits for trigger from module 1, sends SCANADVD,
waits for VMC, sends trigger to module 3.
Module 3 Waits for trigger from module 2, switches, sends
SCANADVD, waits for VMC, sends trigger to module1.
This method allows modules to communicate as to when to start switching
as well as telling the measurement device when the switches have settled.
This guarantees no channel contentions while switching.