Chapter 3
Hardware Overview
3-10
ni.com
Figure 3-10.
PLL Block Diagram
Correlated Digital I/O
The NI 6115/6120 contains eight lines of DIO for general-purpose use.
You can software-configure groups of individual lines for either input or
output. The NI 6115/6120 includes a FIFO for buffered operation. This
operation allows you to read/write an array of data, using either an internal
or external clock source, at a maximum rate of 10 MHz. In addition, you
can correlate DIO and AI/AO operations to the same clock. Refer to the
Correlating DIO Signal Connections
, for information on which signals you can use to clock DIO
operation. At system startup and reset, the DIO ports are all
high-impedance.
The hardware up/down control for general-purpose counters 0 and 1 are
connected onboard to DIO6 and DIO7, respectively. Thus, you can use
DIO6 and DIO7 to control the general-purpose counters. The up/down
control signals, GPCTR0_UP_DOWN and GPCTR1_UP_DOWN, are
input only and do not affect the operation of the DIO lines.
Timing Signal Routing
The DAQ-STC provides a flexible interface for connecting timing signals
to other devices or external circuitry. The NI 6115/6120 uses the RTSI bus
to interconnect timing signals between devices, and it uses the
programmable function input (PFI) pins on the I/O connector to connect the
device to external circuitry. These connections are designed to enable the
NI 6115/6120 to both control and be controlled by other devices and
circuits.
There are 13 timing signals internal to the DAQ-STC that can be controlled
by an external source. These timing signals can also be controlled by
signals generated by the DAQ-STC, and these selections are fully software
Phase Comp
Div/10
Div/60
VCXO
60 MHz out
synched to 10 MHZ
backplane clock
Loop
Filter
+
–
PXI Bus
10 MHz
