Chapter 3
Hardware Overview
©
National Instruments Corporation
3-13
PCI-4451/4452/4453/4454 User Manual
Table 4-6,
, shows that there is a 50 k
Ω
pull-up resistor. This
pull-up resistor sets the DIO0 pin to a logic high when the output is in a high-impedance
state. Take careful consideration of the power-on state of the system to prevent any damage
to external equipment.
Timing Signal Routing
♦
PCI-4451/4452
The DAQ-STC provides a flexible interface for connecting timing signals
to other devices or to external circuitry. Your PCI-4451/4452 uses the RTSI
bus to interconnect timing signals between devices, and uses the PFI pins
on the I/O connector to connect the device to external circuitry. These
connections enable the PCI-4451/4452 to both control and be controlled by
other devices and circuits.
There are a total of 13 timing signals internal to the DAQ-STC that you can
control by an external source. You can also control these timing signals by
signals generated internally to the DAQ-STC, and these selections are fully
software configurable. Many of these timing signals are also available as
outputs on the RTSI pins, as indicated in the
section of this
chapter, and on the PFI pins, as indicated in Chapter 4,
♦
PCI-4453/PCI-4454
Your PCI-4453/4454 uses the RTSI bus to interconnect timing signals
between devices. The RTSI bus enables the PCI-4453/4454 to both control
and be controlled by other devices.
Programmable Function Inputs (PCI-4451/4452 Only)
The 10 PFIs connect to the signal routing multiplexer for each timing
signal, and software can select one of the PFIs as the external source for a
given timing signal. You can use any of the PFIs as an input for any of the
timing signals and multiple timing signals can use the same PFI
simultaneously. This flexible routing scheme reduces the need to change
physical connections to the I/O connector for different applications. You
can also individually enable each of the PFI pins to output a specific
internal timing signal. For example, if you need the GPCTR0_SOURCE
signal as an output on the I/O connector, software can turn on the output
driver for the PFI8/GPCTR0_SOURCE pin.
Note
Two of the 10 PFI pins are not available for general-purpose input on the digital
connector. You can configure PFI2/CONVERT* and PFI5/UPDATE* as outputs only.
