Refer to the following sections for information about the analog bus on your NI SwitchBlock carrier and how to use it.

Basics

Each carrier has an analog bus that you can use to make connections between cards that compose a multicard device, between devices in the same carrier, or between devices in different carriers when the NI 2806 expansion bridge is installed.

NI SwitchBlock devices contain analog bus channels used to connect to the analog bus on the carrier. To connect a row on a card to the analog bus on the carrier, connect the row to the analog bus channel of the same number on the device.

Note   The carrier analog bus lines are not channels in software. To connect your device to the analog bus, connect a row to an analog bus channel.
Note   Analog bus channels on 1-wire cards connect to a single line on the analog bus, while analog bus channels on 2-wire cards connect to two lines on the analog bus.

Because all cards in a carrier share the analog bus, multiple devices cannot connect to the same analog bus line simultaneously unless they are both of the same wire mode and you allow multiple devices to connect to the same analog bus lines using the Analog Bus Sharing Enable property or the NISWITCH_ATTR_ANALOG_BUS_SHARING_ENABLE attribute.

Note   Enabling and disabling analog bus sharing protects the user from inadvertently connecting to the same analog bus lines when you use the immediate VIs/functions, but it does not provide additional protection when you manipulate relays directly using the niSwitch Relay Control VI or the niSwitch_RelayControl function. NI does not recommend manipulating relays directly when multiple NI SwitchBlock devices connect to the analog bus.

Connecting Signals Between Cards in a Multicard Device

You can use analog bus channels to route signals between the cards that compose a multicard device. The following image illustrates signal connections to connect channels c0 and c43 in a multicard device composed of two cards.

Complete the following steps to connect signals between cards in the same device:

  1. Determine which channels you want to connect.
  2. Set all channels between the channels selected in Step 1, including the analog bus channels, as reserved for routing.
    Note   You can set a channel as reserved for routing only if it is not already in use and its Analog Bus Sharing Enable property is set to FALSE.
  3. Connect the channels selected in Step 1 through any channels necessary to route the signals. Refer to the previous figure for an example of routing to connect c0 to c43 in a device composed of two NI 2810 cards.

Connecting Signals Between Devices

You can use the analog bus to route signals between multiple NI SwitchBlock devices with the same wire mode, whether the devices are installed in the same carrier or installed in separate carriers connected by the NI 2806 expansion bridge. The following image illustrates signal connections to connect channel c44 in a multicard device installed in one carrier to channel c0 in a single-card device installed in an adjacent carrier connected by the NI 2806 expansion bridge.

Complete the following steps to connect signals between multiple devices:

  1. Verify that the devices are of the same wire mode.
  2. If the devices you would like to connect are in separate carriers, verify that the NI 2806 expansion bridge has been installed.
  3. Determine which analog bus channels, such as ab0, you want to connect signals to on each of the devices.
  4. Enable an analog bus channel on each of the devices to be shared across devices using the Analog Bus Sharing Enable property or the NISWITCH_ATTR_ANALOG_BUS_SHARING_ENABLE attribute. Refer to the Basics section of this topic to determine which analog bus channel on each device corresponds to the analog bus line you would like to share.
    Note   Analog bus channels can be shared only when the corresponding analog bus lines are not already in use. The analog bus channels on a 1-wire device connect to a single analog bus line each, while the analog bus channels on a 2-wire device connect to two lines each.
  5. Reserve for routing any channels needed to connect the channels selected in Step 3 to the analog bus channel that will share the analog bus line.
    Note   A channel that shares an analog bus line cannot be reserved for routing, and a channel that has been reserved for routing cannot share an analog bus line.
  6. For each device, connect the channels selected in Step 3 to the analog bus channel that will share the analog bus line through any channels selected in Step 4. For example, to connect c44 on Device 1 to c0 on Device 2 in the system shown in the previous image, you would need to route signals between c44 and ab2 on Device 1 and between c0 and ab2 on Device 2.

Related Information:

  • Analog Bus Sharing Enable Property
  • Analog Bus Sharing Enable Attribute
  • niSwitch Properties