Chapter5 SignalConnections
©NationalInstruments Corporation 5-15 7344/7334Hardware User Manual
The32-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.
Alldigital I/O lines have programmable direction and polarity. Each output
circuitcan sink and source 24 mA.
The state of the input pins at power-upis controlled by the DPull pin.
ConnectingDPull to +5 Vor leaving it unconnected configures all pins in
all ports for 100 kΩpull-ups. Connecting DPull to ground configures the
ports for 100 kΩ pull-downs.

PWM Features

The 7344/7334 controllers provide two pulse width modulation (PWM)
outputs on the digital I/O connector. The PWM outputs generate periodic
waveformswhose perio d and duty cycles can be independently controlled
through software commands. You can think of PWM as a digital
representationof ananalog value,because the d uty cycleis directly
proportional to the desired output value. PWM outputs are typically used
fortransmitting an analog value throug h an optocoupler. A simple lowpass
filterturns a PWM signal back into its corresponding analog value. If
desired,y ou can use the PCLK input instead of the internal source as the
clock for the PWM generators.
Note Thesesignals are not associated in any way with the PID servo control loop; they are
configuredin so ftware. Refer to your FlexMotion Software Reference Manual for more
information.
RTSI Connector
Thephysical RTSI bus interface varies depending on the type of 7334/7334
controller.
Forthe PCI-7344 and PCI-7334, the RTSI bus is connected with a ribbon
cable acrossNational Instruments PCI devices with RTSI capability.
TheFW-7344 RTSIbus is connected with an external 14-pin shielded cable
acrossNational Instruments distributed devices with RTSI capability.
The PXI-7344 requires no extracable, because the PXI busdirectly
connectsthe RTSIbus across all National Instruments PXI devices.