User manual

Chapter 3 Software Overview
© National Instruments Corporation 3-97 NI-DAQ User Manual for PC Compatibles
GPCTR_Change_Parameter(deviceNumber, ND_CLOCK_x,
ND_SYNCHRONIZATION_METHOD, ND_PULSE_PER_SECOND)
GPCTR_Change_Parameter(deviceNumber, ND_CLOCK_x,
ND_SECONDS,lastTime)
GPCTR_Control(deviceNumber, ND_CLOCK_x, ND_PROGRAM)
Comment: We have programmed the clock. Now we need to
Comment: make sure that the Comment: programming was
Comment: really successful.
timeAfterProgramming = Satellite Receiver Time
if (timeAfterProgramming = lastTime)
{
Comment: We were successful in programming the clock in
Comment: time!
}
else
{
Comment: We didn't make it in time. Try again…
}
}
IRIG
The Inter Range Instrumentation Group (IRIG) defines a series of
time-code protocols, which transmit a series of data frames that provide
timing information in the binary data of the frame as well as at the start of
frame time. The clock synchronization uses a subset of the IRIG-B protocol
for synchronization. The IRIG-B frame consists of 100 bits, each of which
is pulse-width modulated for 10 ms. The resulting data stream repeats once
per second with the beginning of the frame marking the 1 second epoch
(See Figure 3-38).