USB-CTR datasheet(3/8 Pages) ETC

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Measurement Computing

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USB-CTR Series

Features

Non-recycle: The counter freezes if the max limit or min limit

is reached.

• When counting up, the counter stops when the max limit

is reached.

• When counting down, the counter stops when the min

limit is reached.

Counting resumes if the direction is reversed or if the counter is

reloaded with a value between max limit and min limit.

CountDown: Enables count down mode. This mode is overrid-

den by the state of the gate input if the gate is programmed for

direction control.

Output On: Enables counter output mode. By default, the coun-

ter output goes high when the counter reaches the value of

output register 0, and low when the counter reaches the value

of output register 1.

Output Initial State: Sets the initial state of the counter output

to either high or low.

Direction Control: Allows the counter input connector (CxIN) to

act as the pulse source and the counter gate connector (

CxGT)

to act as the direction. By default, the counter increments when

CxGT=1 (high), and decrements when CxGT=0 (low).

Gating: Allows the counter gate connector (CxGT) to gate the

counter. By default, the counter is enabled when the

CxGT signal

is high. When the

CxGT signal is low, the counter is disabled,but

holds the count value.

Clear/Reload: Clears the count to zero unless counting in Range

Limit mode. If counting in Range Limit mode, the counter gate

signal reloads the counter from the min limit register.

Count Trigger: The counter starts counting when the counter

gate signal goes active. By default, active is on the rising edge.

Period Measurement Mode

In period measurement mode, a USB-CTR Series device measures

the period of any signal at a counter input (

CxIN). The device

counts the integral number of ticks that make up the period,

and the data returned is always time measured in ticks.

The measurement period is the time from edge-to-edge, either

both rising or both falling. Period data is latched as it becomes

available, and is acquired at the counter read rate.

The data returned is interpreted as time measured in ticks. This

data represents the number of tick size intervals counted during

the period measurement.

Optionally, the counter gate connector (

CxGT) can be used to

gate the counter.

• When

CxGT is high, the counter is enabled.

• When

CxGT is low, the counter is disabled, but holds the

count value.

The 96 MHz system clock is used as the timing source. Periods

from sub-microsecond to many seconds can be measured.

The following period measurement mode options are software-

selectable:

Period mode: Select one of the following period modes:

• X1 – The measurement is latched each time one complete

period is observed.

• X10 – The measurement is latched each time 10 complete

periods are observed.

• X100 – The measurement is latched each time 100 com-

plete periods are observed

• X1000 – The measurement is latched each time 1000 com-

plete periods are observed.

Tick size: The tick size (or period resolution) is a fundamental

unit of time derived from the period of the 96 MHz system clock.

Four counter channel tick sizes are available – 20.83 ns, 208.3

ns, 2083.3 ns, and 20833.3 ns.

Pulse Width Measurement Mode

In pulse width measurement mode, a USB-CTR Series device

measures the time from the rising edge to the falling edge, or

vice versa, on a counter input signal (

CxIN). The measurement

is either pulse width low or pulse width high, depending upon

the edge detection setting.

Every time the pulse width measurement is latched from the

counter, the counter is immediately cleared and enabled to count

the time for the next pulse width. The pulse width measurements

are latched as they become available.

The data returned is interpreted as time measured in ticks. This

data represents the number of tick size intervals counted during

the pulse width measurement.

Optionally, the counter gate connector (

CxGT) can be used to

gate the counter.

• When

CxGT is high, the counter is enabled.

• When

CxGT is low, the counter is disabled, but holds the

count value.

The 96 MHz system clock is used as the timing source. Pulse

widths from sub-microsecond to many seconds can be measured.

Tick size: The tick size (or pulse width resolution) is a fundamen-

tal unit of time derived from the period of the 96 MHz system

clock. Four counter channel tick sizes are available – 20.83 ns,

208.3 ns, 2083.3 ns, and 20833.3 ns.

Timing Mode

In timing mode, a USB-CTR Series device measures the time

between an event on the counter input (

CxIN) and a subsequent

event on the counter gate (

CxGT), such as the rising or falling

edge of one event with respect to the rising or falling edge of

another event (based on the edge detection setting).

Whenever the time measurement is latched from the counter,

the counter is immediately cleared and enabled for accepting

the subsequent time period, which starts with the next edge on

the main channel.

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