Chapter 2
NI 2565 Operation
2-4
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National Instruments Corporation
General Purpose Relays
The general-purpose relay consists of 16 channels (CH0 through CH15).
Each channel has a corresponding common (COM0 through COM15).
Each channel connects to the corresponding common by closing its relay.
The relay name is based on the corresponding signal name. For example,
the relay connecting CH9 to COM9 is CH9. You can have multiple
channels connected to the corresponding commons simultaneously.
See Appendix C,
, for an illustration of the
NI 2565 architecture.
The NI 2565 relays are single-side stable. When power is removed from the
relay coil, the relay returns to its de-energized state. The de-energized state
opens all the relays, disconnecting each channel signal from its
corresponding common.
Switch Control Circuitry
The switch control circuitry (SCC) is responsible for opening and closing
relays on the NI 2565. You can load commands for the SCC into memory
storage using the driver software you received with your kit. Consult the
online help or your software documentation for specific information on the
appropriate commands. There are two reasons for storing the commands in
memory before the SCC can process them:
•
The operate and release times for the NI 2565 are 10 ms and 5 ms,
respectively. Using memory storage, the software can send multiple
commands to the SCC without having to wait for a relay action
to complete.
•
The memory is used to store a scan list necessary for hardware
random scanning.
Random Scanning
The NI 2565 can perform random scanning. In random scanning,
the switch card can open or close relays in any order.
The scan list is downloaded to onboard memory. Commands in the scan
list can:
•
Open or close relays
•
Wait for an external trigger