Digital I/O
The NI PXIe-7821R provides connections for 128 digital input/output (DIO) channels.
Connectors 0 through 3 each contain 32 high-speed DIO channels that can run up to 80 MHz
signal frequencies. Each connector has selectable logic levels that you can configure as 1.2 V,
1.5 V, 1.8 V, 2.5 V, or 3.3 V. You can configure each channel as input or output.
Figure 4.
Connecting to the DIO Channels
NI PXIe-7821R
Power
FPGA
Connection
Accessory
DIO0
DIO1
DIO30
DIO31
Connector X (DIO)
1
2
1. High-speed signal frequencies up to 80 MHz with logic levels configured as 1.2 V, 1.5 V, 1.8 V, 2.5 V, or
3.3 V
2. LED
The DIO channels connect to the FPGA through protection circuitry, which has overvoltage
and undervoltage protection as well as overcurrent protection. Refer to the
NI PXIe-7821R
Specifications
for more information about the maximum voltage and current.
When the system powers on, the DIO channels are set as input low with pull-down resistors.
To set another power-on state, you can configure the NI PXIe-7821R to load a VI when the
system powers on. The VI can then set the DIO lines to any power-on state.
All the DIO channels on Connectors 0 through 3 are routed with a 50 Ω characteristic trace
impedance. Route all external circuitry with a similar impedance to ensure best signal quality.
NI recommends performing signal integrity measurements to test the affect of signal routing
with the cable and connection accessory for your application.
Installing Noise Suppression Ferrites
Caution
To ensure the specified EMC performance, operate this product only with
shielded cables and accessories. Do not use unshielded cables or accessories unless
they are installed in a shielded enclosure with properly designed and shielded input/
output ports and connected to the product using a shielded cable. If unshielded
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NI PXIe-7821R Getting Started Guide
