Barracuda RV8 Manual - page 8
4-20
System 3
RV8 Barracuda
sample period in seconds that you require and then divide by 1/(sample period).
These circuits work only with the Barracuda. If the circuit is run on a different RP
module it will give the following error:
RP Control Object files (RCO) will produce similar problems. If you attempt to run
an RCO file (compiled RPvdsEx files for use with ActiveX controls and turn-key
software programs) that has an arbitrary sample rate on another RP device the
same error will occur.
Using the TimeStamp Component
The TimeStamp component is an event timer with submicrosecond accuracy. With
other RP systems the resolution of the TimeStamp is no better than the sample clock
period. TimeStamp uses the system clock to determine when, within a sample period,
the event occurred. After each sample period the TimeStamp component is reset.
The diagram below shows how TimeStamp works. The first event occurs 2.2
microseconds after the start of the first sample period so a value of 2.2 is
generated. The second event occurs 7.04 microseconds after the start of the second
sample period so a value of 7.04 is generated.
TimeStamp Diagram
The circuit below saves the event time (in microseconds) to a SerStore buffer. The
circuit has two parameter tags:
InputBit
and
data
. The InputBit tag sends the digital
input channel number (to which the Event trigger will be sent) to the TimeStamp.
This determines which of the Barracuda's digital input lines will be monitored for
triggers. The
data
tag reads the stored event-time data to a PC buffer.
A software trigger resets the SimpCount, starting the clock, and will also reset the
TimeStamp component and the SerStore buffer. The SimpCount increments the count
value at every sample tick. The ScaleAdd divides the SimpCount output by the
sample period (40.96 microseconds) to keep track of the time in milliseconds.
When an event is detected, the TimeStamp output is added to the SimpCount output
to get the event time in microseconds.