The SPI Rack is backwards compatible with most of the IVVI Rack modules, provided that the B1a (breakout) module is used. In the IVVI rack, the control signals are analog DAC outputs routed over the backplane. These lines are not present in the SPI Rack. The B1a and B2b modules remedies this by bringing these control lines of two neighboring modules to the front of the rack or directly to an ADC. One B2b can connect to two measurement modules, and one B1a can connect to either:
The B1a/B2b cannot be placed at any position in the rack, as the backplane has specific routing to accommodate this backwards compatibility. It has to be placed in slot 2, 5, 8 or 11. See the image below for exact positions (red arrows).
This image also shows two different use cases: one with two VIb modules (integrated source/measure) and one with a VIb and a M2m module. For the VIb modules only the two B1a inputs are used as they have their own isolated outputs. The M2m module uses the isolated output of the B1a module.
The module has two inputs going to the module left of it and two to the right. One of these inputs is not isolated, this one is meant to be connected to a DAC module (D5a) that is present in the SPI Rack. The other input is isolated, this one can be connected to any external device like a lock-in. There is one isolated output which is connected to either the module left or right of the B1a. This is determined by the routing in the module and can be changed. The arrow on the front of the module indicates which module it is connected to. For more information, see the B1a module page page.