USB-CAN
This topic describes the hardware characteristics of the USB-CAN hardware.
USB-8473/USB-8473s: High-Speed Physical Layer
The USB-CAN physical layer circuitry interfaces the CAN protocol controller to the physical bus wires. The USB-CAN High-Speed physical layer is powered internally from the USB through a DC-DC converter, and is optically isolated up to 500 VDC (withstand, 2s max) channel-to-bus. This isolation protects your NI-CAN hardware and the PC it is connected to from being damaged by high-voltage spikes on the CAN bus.
Transceiver
USB-CAN High-Speed hardware uses the Philips TJA1041 High-Speed CAN transceiver. The TJA1041 is fully compatible with the ISO 11898 standard and supports baud rates up to 1 Mbps. This device also supports advanced power management through a low-power sleep mode. This feature is provided as the Transceiver Mode attribute of the Frame API. For detailed TJA1041 specifications, refer to the Philips TJA1041 data sheet.
Bus Power Requirements
Because the High-Speed physical layer is completely internally powered through USB, there is no need to supply bus power. The V signal serves as the reference ground for the isolated signals. Refer to High-Speed PCI, PXI, and USB Connector Pinout for information about how to connect signals to a High-Speed CAN interface.
LED Indicators
The following table provides a description of the LEDs on the front panel of the USB-8473 and USB-8473s.
| Name | Function |
|---|---|
| USB | Indicates connectivity to a USB Host. Green indicates a USB full speed connection. Amber indicates a USB high speed connection. |
| CAN | Flashes to indicate the presence of traffic on the CAN bus. |
USB-8472/USB-8472s: Low-Speed/Fault-Tolerant Physical Layer
The USB-CAN Low-Speed/Fault-Tolerant physical layer is powered internally from the USB through a DC-DC converter, and is optically isolated up to 500 VDC (withstand, 2s max) channel-to-bus. This isolation protects your NI CAN hardware and the PC it is connected to from being damaged by high-voltage spikes on the CAN bus.
Transceiver
USB-CAN Low-Speed/Fault-Tolerant hardware uses the Philips TJA1054A Low-Speed CAN transceiver. The TJA1054A supports baud rates up to 125 kbps. The transceiver can detect and automatically recover from the following CAN bus failures:
- CAN_H wire interrupted
- CAN_L wire interrupted
- CAN_H short-circuited to battery
- CAN_L short-circuited to battery
- CAN_H short-circuited to VCC
- CAN_L short-circuited to VCC
- CAN_H short-circuited to ground
- CAN_L short-circuited to ground
- CAN_H and CAN_L mutually short-circuited
The TJA1054A supports advanced power management through a low-power sleep mode. This feature is provided as the Transceiver Mode attribute of the Frame API. For detailed specifications about the TJA1054A, refer to the Philips TJA1054 data sheet.
Bus Power Requirements
Because the Low-Speed/Fault-Tolerant physical layer is completely powered internally through USB, there is no need to supply bus power. The V signal serves as the reference ground for the isolated signals. Refer to Low-Speed/Fault-Tolerant PCI, PXI, and USB Connector Pinout for information about how to connect signals to a Low-Speed/Fault-Tolerant CAN interface.
LED Indicators
The following table provides a description of the LEDs on the front panel of the USB-8472 and USB-8472s.
| Name | Function |
|---|---|
| USB | Indicates connectivity to a USB Host. Green indicates a USB full speed connection. Amber indicates a USB high speed connection. |
| CAN | Flashes to indicate the presence of traffic on the CAN bus. |