Measurement Computing WBK17 - Manual (Page 11)

WBK17, Counter/Encoder Module 987996 WBK17, pg. 11
Terms Applicable to Counter Modes
The following terms and definitions are provided as an aid to understanding counter modes.
Detection Signal: A detection signal is one of 8 outputs of the pattern detection module. Each input
channel has an associated detection signal (Detect 1 for Channel 1, Detect 2 for Channel 2, etc.) A
channel’s detection signal will go active high when that channel’s counter value meets the setpoint criteria
programmed into the pattern detection module. Detection signals can be scanned along with any other
channel in the scan group.
Gating: Any counter can be gated by the mapped channel. When the mapped channel is high, the counter
will be allowed to count, when the mapped channel is low, the counter will not count but hold its value.
Mapped Channel: A mapped channel is one of 16 signals that can get multiplexed into a channel’s
counter module. The mapped channel can participate with the channel’s input signal by gating the counter,
clearing the counter, etc. The 16 possible choices for the mapped channel are the 8 input signals (post
debounce) and the 8 detection signals.
Start of Scan: The start of scan is a signal that is internal to the WBK17. It signals the start of a scan
group and therefore pulses once every scan period. It can be used to clear the counters and latch the counter
value into the acquisition stream.
Terminal Count: This signal is generated by the counter value. There are only two possible values for
the terminal count: 65,535 for a 16-bit counter (Counter Low); and 4,294,967,295 for a 32-bit counter
(Counter High). The terminal count can be used to stop the counter from rolling over to zero.
Ticksize: The ticksize is a fundamental unit of time and has four possible settings: 20ns, 200ns, 2000ns,
20000ns. For measurements that require a timebase reference like period or pulsewidth, the ticksize is the
basic unit of time. The count value returned in the scan is the number of ticks that make up the time
measurement.
Counter Options
The following mode options are available with the WBK17 and are detailed in the upcoming pages.
A separate block diagram has been created for each mode. Note that the OPT numbers relate to
sections of the block diagrams.
Counter/Totalize Mode (see page 12):
OPT0: Selects totalize or clear on read mode.
OPT1: Determines if the counter is to rollover or “stop at the top.”
OPT2: Determines whether the counter is 16-bits (Counter Low); or 32-bits (Counter High).
OPT3: Determines which signal latches the counter outputs into the data stream back to the
WaveBook. Start of scan or mapped channel.
OPT4: Allows the mapped channel to gate the counter.
OPT5: Allows the mapped channel to decrement the counter.
OPT6: Allows the mapped channel to increment the counter.
Period Mode (see page 14):
OPT[1:0]: Determines the number of periods to time, per measurement (1, 10, 100, 1000).
OPT2: Determines whether the period is to be measured with a 16-bit (Counter Low);
or 32-bit (Counter High).
OPT4: Allows the mapped channel to gate the counter.
OPT6: Allows the mapped channel to be measured for periods.
Pulsewidth Mode (see page 17):
OPT2: Determines whether the pulsewidth is to be measured with a 16-bit counter (Counter Low);
or a 32-bit counter (Counter High).
OPT4: Allows the mapped channel to gate the counter.
OPT6: Allows the mapped channel to be measured for pulsewidth.