I have a PCI computer card that has the following pinouts for CAN communications.
CAN_L CAN_H SHIELD V+ V-
Its a modicon type connector. I know what the CAN_L and CAN_H is for, however I have no clue where to hook the other three SHIELD, V+, V- to on my circuit.
I was told the V+, V- is for external power, but I disabled it through a jumper. However I am wondering if I have to tie it to something. If so what would it be? Any idea?
PS: The card is a National Instruments PCI-CAN card (from 1997)
Connect the SHIELD pin to the shield around the CAN_L/CAN_H twisted-pair.
Probably not.
Don't know about the expensive National board, but assume it doesn't need the V+ and V-. These are optional power pins to power up the transceiver and opto couplers. Most Interfaces are powering these parts from the other side, from the PC logic. And your Shield pin guess what it is for - for shielding your twisted signale lines CAN_H and CAN_L. You should have a look at:
The only use of the V+ and V- pins is to provide suitable voltages for the "fail safe" termination, i.e. pulling the lines to the recessive state, when no device is driving the bus to a dominant state.
Paul
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