National Instruments Data Acquisition Device E Series - Manual (Page 114)

Chapter 5 Counters
© National Instruments Corporation 5-9 E Series User Manual
• Ctr1InternalOutput drives the CTR 1 OUT pin to trigger or control
external devices.
• Ctr1InternalOutput can drive other internal signals.
Refer to Device Routing in MAX in the NI-DAQmx Help or the
LabVIEW 8.x Help for more information.
Counter 1 Up/Down Signal
You can externally input this signal on the P0.7 pin, but it is not available
as an output on the I/O connector. When you enable externally controlled
count direction, Counter 1 counts down when this pin is at a logic low and
counts up when it is at a logic high. If you do not enable externally
controlled count direction, the P0.7 pin is free for general use.
Frequency Output Signal
This signal is available only as an output on the FREQ OUT pin. The
frequency generator for the device outputs on the Frequency Output signal.
The frequency generator is a 4-bit counter that can divide its input clock by
the numbers one through 16. The input clock of the frequency generator is
software-selectable from the internal 10 MHz and 100 kHz timebases. The
output polarity is software-selectable. This output is set to high-impedance
at startup.
Master Timebase Signal
The Master Timebase (MasterTimebase) signal, or Onboard Clock, is the
timebase from which all other internally generated clocks and timebases on
the board are derived. It controls the timing for the analog input, analog
output, and counter subsystems. It is available as an output on the I/O
connector, but you must use one or more counters to do so.
The maximum allowed frequency for the MasterTimebase is 20 MHz, with
a minimum pulse width of 23 ns high or low. There is no minimum
frequency limitation.
The two possible sources for the MasterTimebase signal are the internal
20MHzTimebase signal or an external signal through RTSI 7. Typically the
20MHzTimebase signal is used as the MasterTimebase unless you wish to
synchronize multiple devices, in which case, you should use RTSI 7. Refer
to Chapter 8,
Real-Time System Integration Bus (RTSI) , for more
information about which signals are available through RTSI.