Solution
Digital logic compatibility varies between R Series cards. The following table summarizes the supported logic levels.
| Device | Supported Logic Levels |
|---|
| USB-78xxR, PXIe-78xxR, PCIe-782xR | 3.3 V, 2.5 V, 1.8 V, 1.5 V, 1.2 V |
PXI-78xxR, PCI-78xxR, PCIe-781xR,
PCIe-784xR, PCIe-785xR | 5 V, 3.3 V (see note below) |
USB-78xxR, PXIe-78xxR, and PCIe-782xR devices can receive a maximum input voltage of 3.6 V as described in their specification documentation. These devices have software-selectable logic levels as listed above.
PXI-78xxR, PCI-78xxR, PCIe-781xR, PCIe-784xR, and PCIe-785xR devices are only compatible with 5 V and 3.3 V digital logic levels. These devices can receive signals from 3.3 V or 5 V TTL or CMOS devices. They may also drive signals to 3.3 V or 5 V TTL devices and 3.3 V CMOS devices. They
cannot directly drive a signal to a 5 V CMOS device. The V
oh of the PXI-78xxR, PCI-78xxR, PCIe-781xR, PCIe-784xR, and PCIe-785xR is not high enough to guarantee a valid logic high at the receiving device, so you must add an external pull-up resistor to 5 V on the digital output line. Please see the user manual for more information.