National Instruments 7340 PCI Benutzerhandbuch

The 32-bit digital I/O port is configured in hardware as four 8-bit digital I/O 
ports. The bits in a port are typically controlled and read with byte-wide 
bitmapped commands.

All digital I/O lines have programmable direction and polarity. Each output 
circuit can sink and source 24 mA.

The DPull pin controls the state of the input pins at power-up. Connecting 
DPull to +5 V or leaving it unconnected configures all pins in all ports for 
100 k

Ω pull-ups. Connecting DPull to ground configures the ports for 

100 k

Ω pull-downs.

The 7340 provides two pulse width modulation (PWM) outputs on the 
digital I/O connector. The PWM outputs generate periodic waveforms 
whose period and duty cycles can be independently controlled through 
software commands. The PWM is comparable to a digital representation of 
an analog value because the duty cycle is directly proportional to the 
expected output value. PWM outputs are typically used for transmitting an 
analog value through an optocoupler. A simple lowpass filter turns a PWM 
signal back into its corresponding analog value. You have the option to use 
the PCLK input instead of the internal source as the clock for the PWM 
generators.

These signals are configured in software and are in no way associated with the 

PID servo control loop. Refer to the NI-Motion User Manual for more information.

The physical RTSI bus interface varies depending on the type of 7340 
controller.

The PXI-7340 uses the PXI chassis backplane to connect to other 
RTSI-capable devices.

The PCI-7340 uses a ribbon cable to connect to other RTSI-capable PCI 
devices.