Measurement Computing USB-4301 User manual

USB-4301
9513-based Counter/Timer
User's Guide
Document Revision 5, March, 2009
© Copyright 2009, Measurement Computing Corporation

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HM USB-4301.doc
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HM USB-4301.doc
Table of Contents
Preface
About this User's Guide ....................................................................................................................... 7
What you will learn from this user's guide ......................................................................................................... 7
Conventions in this user's guide ........................................................................................................................................ 7
Where to find more information ......................................................................................................................... 7
Chapter 1
Introducing the USB-4301 .................................................................................................................... 8
Software features ................................................................................................................................................ 8
Connecting a USB-4301 to your computer is easy ............................................................................................. 8
Chapter 2
Installing the USB-4301 ........................................................................................................................ 9
What comes with your USB-4301 shipment? ..................................................................................................... 9
Hardware .......................................................................................................................................................................... 9
Additional documentation ................................................................................................................................................. 9
Unpacking the USB-4301 ................................................................................................................................. 10
Installing the software ...................................................................................................................................... 10
Installing the USB-4301 ................................................................................................................................... 10
Chapter 3
Functional Details ............................................................................................................................... 11
USB-4301 block diagram ................................................................................................................................. 11
External components ........................................................................................................................................ 12
USB connector .................................................................................................................................................................12
Status LED .......................................................................................................................................................................12
Power LED ......................................................................................................................................................................12
Screw terminal banks .......................................................................................................................................................12
Counter terminals (INP1 to INP5, GAT1 to GAT5, and OUT1 to OUT5) ......................................................................14
Digital input (DI0 to DI7) and output (DO0 to DO7) terminals .......................................................................................14
Digital input control terminal (DI CTL) for pull-up/down configuration ........................................................................15
Interrupt input terminal (INT) ..........................................................................................................................................15
Oscillator output terminal (OSC) .....................................................................................................................................15
Ground terminals (GND) .................................................................................................................................................15
Oscillator output (OSC) .................................................................................................................................... 15
Internal sources ................................................................................................................................................................15
External sources ...............................................................................................................................................................16
Divider (OSC divider)......................................................................................................................................................16
Counter operation ............................................................................................................................................. 16
Count source ....................................................................................................................................................................17
Gate control .....................................................................................................................................................................17
Counting modes ................................................................................................................................................ 17
Reload ..............................................................................................................................................................................17
Recycle ............................................................................................................................................................................17
BCD/Binary mode ...........................................................................................................................................................18
The "Special" gate............................................................................................................................................................18
Output control ..................................................................................................................................................................18
Example 1 ........................................................................................................................................................................19
Example 2 ........................................................................................................................................................................19
Interrupt input pin (INT) ................................................................................................................................... 20

USB-4301 User's Guide About this User's Guide
6
Chapter 4
Specifications ...................................................................................................................................... 21
Counter ............................................................................................................................................................. 21
Digital input / output ......................................................................................................................................... 22
Interrupt Input ................................................................................................................................................... 22
Memory ............................................................................................................................................................ 23
Microcontroller ................................................................................................................................................. 23
USB +5V voltage ............................................................................................................................................. 23
LEDs ................................................................................................................................................................. 23
Power ................................................................................................................................................................ 23
USB specifications ........................................................................................................................................... 24
Environmental .................................................................................................................................................. 24
Mechanical ....................................................................................................................................................... 24
Screw terminal connector type and pin out....................................................................................................... 24
Screw terminal pin out ...................................................................................................................................... 25
Declaration of Conformity .................................................................................................................. 26

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HM USB-4301.doc
Preface
About this User's Guide
What you will learn from this user's guide
This user's guide explains how to install, configure, and use the USB-4301 so that you get the most out of its
counter features. This user's guide also refers you to related documents available on our web site, and to
technical support resources.
Conventions in this user's guide
For more information on …
Text presented in a box signifies additional information and helpful hints related to the subject matter you are
reading.
Caution! Shaded caution statements present information to help you avoid injuring yourself and others,
damaging your hardware, or losing your data.
< : > Angle brackets that enclose numbers separated by a colon signify a range of numbers, such as those assigned
to registers, bit settings, etc.
bold text Bold text is used for the names of objects on the screen, such as buttons, text boxes, and check boxes. For
example:
1. Insert the disk or CD and click the OK button.
italic text Italic text is used for the names of manuals and help topic titles, and to emphasize a word or phrase. For
example:
The InstaCal installation procedure is explained in the Quick Start Guide.
Never touch the exposed pins or circuit connections on the board.
Where to find more information
The following electronic documents provide helpful information relevant to the operation of the USB-4301
MCC's Specifications: USB-4301 (the PDF version of the Specifications chapter in this guide) is available
on our web site at www.mccdaq.com/pdfs/Specs/USB-4301-spec.pdf.
MCC's Quick Start Guide is available on our web site at
www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.
MCC's Guide to Signal Connections is available on our web site at
www.mccdaq.com/signals/signals.pdf.
MCC's Universal Library User's Guide is available on our web site at
www.mccdaq.com/PDFmanuals/sm-ul-user-guide.pdf.
MCC's Universal Library Function Reference is available on our web site at
www.mccdaq.com/PDFmanuals/sm-ul-functions.pdf.
MCC's Universal Library for LabVIEW™ User’s Guide is available on our web site at
www.mccdaq.com/PDFmanuals/SM-UL-LabVIEW.pdf.
USB-4301 User's Guide (this document) is also available on our web site at
www.mccdaq.com/PDFmanuals/USB-4301.pdf.

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Chapter 1
Introducing the USB-4301
The USB-4301 is a USB-based high-performance, low-cost counter/timer device.
The USB-4301 is designed with a 9513 counter/timer chip. The 9513 chip has five independent 16-bit counters
(65,536 counts). Each counter has an input source, internal count register, load register, hold register, output,
and gate.
The 9513 is software-programmable for event counting, pulse and frequency measurement, alarm comparisons,
and other input functions. The 9513 can generate frequencies with either complex duty cycles, or with one-shot
and continuous-output modes. You can chain up to five 9513 counters together using software to enable a 32-,
48-, 64-, or 80-bit counter that does not require hardware connections. The gate source and gating functions are
software-programmable.
An eight-bit, high-current digital output port provides logic-level control, and can be used to switch solid state
relays. An eight-bit digital input port can be used to sense contact closures and other TTL level signals.
For more information on the 9513 counter/timer, refer to the 9513 data sheet. This document is available at
www.mccdaq.com/PDFmanuals/9513A.pdf.
Software features
For information on the features of InstaCal and the other software included with your USB-4301, refer to the
Quick Start Guide that shipped with your device. The Quick Start Guide is also available in PDF at
www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf.
Check www.mccdaq.com/download.htm for the latest software version.
Connecting a USB-4301 to your computer is easy
Installing a data acquisition device has never been easier.
The USB-4301 relies upon the Microsoft Human Interface Device (HID) class drivers. The HID class
drivers ship with every copy of Windows that is designed to work with USB ports. We use the Microsoft
HID because it is a standard, and its performance delivers full control and maximizes data transfer rates for
your USB-4301. No third-party device driver is required.
The USB-4301 is plug-and-play. There are no jumpers to position, dual in-line package (DIP) switches to
set, or interrupts to configure.
You can connect the USB-4301 before or after you install the software, and without powering down your
computer first.
When you connect an HID to your system, your computer automatically detects it and configures the
necessary software. You can connect and power multiple HID peripherals to your system using a USB hub.
You can connect your system to various devices using a standard four-wire cable. The USB connector
improves upon serial and parallel port connectors with one standardized plug-and-port combination.
Data can flow two ways between a computer and peripheral over USB connections.

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Chapter 2
Installing the USB-4301
What comes with your USB-4301 shipment?
As you unpack your board, make sure that the following components are included.
Hardware
USB-4301
USB cable (2 meter length)
Additional documentation
In addition to this hardware user's guide, you should also receive the Quick Start Guide (available in PDF at
www.mccdaq.com/PDFmanuals/DAQ-Software-Quick-Start.pdf). This booklet supplies a brief description of
the software you received with your USB-4301 and information regarding installation of that software. Please
read this booklet completely before installing any software or hardware.

USB-4301 User's Guide Installing the USB-4301
10
Unpacking the USB-4301
As with any electronic device, you should take care while handling to avoid damage from static
electricity. Before removing the USB-4301 from its packaging, ground yourself using a wrist strap or by simply
touching the computer chassis or other grounded object to eliminate any stored static charge.
If any components are missing or damaged, notify Measurement Computing Corporation immediately by
phone, fax, or e-mail:
Phone: [phone] and follow the instructions for reaching Tech Support.
Fax: [phone] to the attention of Tech Support
Email: [email protected]
Installing the software
Refer to the Quick Start Guide for instructions on installing the software on the Measurement Computing Data
Acquisition Software CD. This booklet is available in PDF at www.mccdaq.com/PDFmanuals/DAQ-Software-
Quick-Start.pdf.
Installing the USB-4301
To connect the USB-4301 to your system, turn your computer on, and connect the USB cable to a USB port on
your computer or to an external USB hub that is connected to your computer. The USB cable provides power
and communication to the USB-4301.
The USB-4301 installs as a composite device with separate devices attached. When you connect the USB-4301
for the first time, Found New Hardware popup balloons (Windows XP) or dialogs (Windows 2000) display as
each USB-4301 interface is detected.
After the USB-4301 is installed, the Power LED remains lit to indicate that communication is established
between the USB-4301 and your computer.
Caution! Do not disconnect any device from the USB bus while the computer is communicating with the
USB-4301, or you may lose data and/or your ability to communicate with the USB-4301.
If the Power LED turns off
If the Power LED is illuminated but then turns off, the computer has lost communication with the USB-4301.
To restore communication, disconnect the USB cable from the computer, and then reconnect it. This should
restore communication, and the Power LED should turn back on.

11
Chapter 3
Functional Details
USB-4301 block diagram
USB-4301 functions are illustrated in the block diagram shown here.
Screw terminal I/O connector
Interrupt Input
Digital I/O
Digital
input
Digital
output
9513
CTR1 Input
CTR1 Gate
CTR2 Input
CTR2 Gate
CTR2 Output
CTR3 Gate
CTR3 Output
CTR4 Input
CTR4 Gate
CTR4 Output
CTR5 Input
CTR5 Gate
Counter 1
Counter 2
Counter 3
Counter 4
Counter 5
USB
Full-speed
USB 2.0
Compliant
Interface
USB
Microcontroller
Clock
Generator
(7:0)
(7:0)
Screw terminal I/O connector
1.0/1.67/
3.3/5.0 MHZ
12 MHZ
Data Bus
Figure 1. USB-4301 functional block diagram

USB-4301 User's Guide Functional Details
12
External components
The USB-4301 has the following external components, as shown in Figure 2.
USB connector
Status LED
Power LED
Screw terminal banks (2)
USB
connector
Power LED
Status LED
Screw terminal
pins 1 to 28
Screw terminal
pins 29 to 56
Figure 2. USB-4301 components
USB connector
The USB connector provides power and communication. The voltage supplied through the USB connector is
system-dependent, and may be less than 5 V. No external power supply is required.
Status LED
The Status LED indicates the communication status of the USB-4301. It flashes when data is being transferred,
and is off when the USB-4301 is not communicating. This LED uses up to 10 mA of current and cannot be
disabled.
Power LED
The power LED lights up when the USB-4301 is connected to a USB port on your computer or to an external
USB hub that is connected to your computer.
Screw terminal banks
The USB-4301 has two rows of screw terminals—one row on the top edge of the housing, and one row on the
bottom edge. Each row has 28 connections. Use 16 AWG to 30 AWG wire gauge when making screw terminal
connections. Pin numbers are identified in Figure 3.

USB-4301 User's Guide Functional Details
13
Pin 56Pin 29
Pin 28Pin 1
USB-4301
Figure 3. USB-4301 screw terminal pin numbering
Screw terminal – pins 1-28
The screw terminals on the bottom edge of the USB-4301 (pins 1 to 28) provide the following connections:
Two counter input connections (INP1 and INP2)
Two counter gate connections (GAT1 and GAT2)
Two counter output connections (OUT1 and OUT2)
Eight digital input connections (DI0 to DI7)
One pull-up/down control connection (DI CTL)
One oscillator output connection (OSC)
One interrupt input connection (INT)
Two voltage output power connections (+5V)
Two ground connections (GND)
Seven pins are reserved (RSVD). Do not connect signals to these pins.
Screw terminal – pins 29-56
The screw terminals on the top edge of the USB-4301 (pins 29 to 56) provide the following connections:
Three counter input connections (INP3 – INP5)
Three counter gate connections (GAT3 – GAT5)
Three counter output connections (OUT3 – OUT5)
Eight digital output connections (DO0 to DO7)
One pull-up/down control connection (DI CTL)
Two ground connections (GND)
Nine pins are reserved (RSVD). Do not connect signals to these pins.

USB-4301 User's Guide Functional Details
14
29 INP3 30 GAT3 31 OUT3 32 INP4 33 GAT4 34 OUT4 35 INP5 36 GAT5 37 OUT5 38 GND 39 40 41 42 43 44 45 46 47 50 DO1 51 DO2 52 DO3 53 DO4 54 DO5 55 DO6 56 DO7 48 GND 49 DO0
RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD RSVD
INP1 1 GAT1 2 OUT1 3 INP2 4 GAT2 5 OUT2 6 OSC 7 +5V 8 INT 9 GND 10 RSVD 11 +5V 18 DI CTL 19 GND 20 DI0 21 DI1 22 DI2 23 DI3 24 DI4 25 DI5 26 DI6 27 DI7 28
12 13 14 15 16 17
RSVD RSVD RSVD RSVD RSVD RSVD
Figure 4. USB-4301 signal pin out
Counter terminals (INP1 to INP5, GAT1 to GAT5, and OUT1 to OUT5)
The counter terminals provide the connections for the clock input signal and gate signal to each counter, and the
output signal from each counter. The clock, gate, and output sources are software-selectable. You can configure
each counter to count up or down.
Digital input (DI0 to DI7) and output (DO0 to DO7) terminals
You can connect up to eight digital input lines to the screw terminals labeled DI0 to DI7 (pins 21 through 28),
and up to eight digital output lines to the screw terminals labeled DO0 to DO7 (pins 49 through 56).
You can use the digital input terminals to detect the state of any TTL level input. Refer to the schematic shown
in Figure 5. When the switch is set to the +5V input, DI7 reads TRUE (1). If you move the switch to GND, DI7
reads FALSE (0).
+5V
GND
DI
7
Figure 5. Schematic showing switch detection by digital channel DI7
For more information on digital signal connections
For more information on digital signal connections and digital I/O techniques, refer to the Guide to Signal
Connections (available on our web site at www.mccdaq.com/signals/signals.pdf).

USB-4301 User's Guide Functional Details
15
Digital input control terminal (DI CTL) for pull-up/down configuration
All digital input pins are floating by default. When inputs are floating, the state of unwired inputs is undefined
—they may read high or low. You can use the DI CTL connection (pin 19) to configure the inputs to read a high
or low value when they aren’t wired.
To pull up the digital pins to +5 V — inputs read high when unwired — wire the DI CTL terminal pin to a
+5V terminal pin (pin 8 or 18).
To pull down the digital pins to ground — inputs read low when unwired — wire the DI CTL terminal pin
to a GND terminal pin (pin 10, 20, 38, or 48).
The DI CTL connection pulls the inputs to +5V or GND through a 47 k Ω resistor.
Interrupt input terminal (INT)
You can configure the interrupt input terminal (pin 9) with InstaCal to trigger off rising or falling edge inputs.
You can program this pin to perform the following tasks:
Send an event notification to the computer. The transfer rate is system-dependent.
Latch in the digital inputs. With this option, the current value of the digital inputs (0 or 1) is read and
stored. The stored value is updated when an active edge occurs on this pin.
Latch out the digital outputs. With this option, digital outputs are not set to the value written until an active
edge occurs on this pin.
Save the current value of a counter. You can configure this option for each counter individually.
Oscillator output terminal (OSC)
The oscillator output terminal (pin 7) outputs a configurable clock frequency. You can select the source of the
oscillators and also select dividers for the oscillators programmatically to set the output rate.
Ground terminals (GND)
The ground (GND) connections (pin 10, 20, 38, or 48) provide a common ground for the digital and voltage
output connections.
Oscillator output (OSC)
You can set the oscillator input programmatically to one of five internal frequency sources or one of 10 external
input pins. The oscillator output can be divided by any number from 1 to 16 before being output to the OSC pin.
Internal sources
The base frequency for the internal frequency sources can be set through InstaCal to one of four different
frequencies — 1.0000 MHz, 1.6667 MHz, 3.3333 MHz, or 5.0000 MHz. This base frequency is used to
generate the five internal frequency sources — FREQ1 through FREQ5.
FREQ1 is the same as the base frequency and each successive internal frequency following FREQ1 divides the
base frequency by another multiple of 10, for example FREQ2 is the base frequency divided by 10, FREQ3 is
the base frequency divided by 100, and so on. This is illustrated in the following table.

USB-4301 User's Guide Functional Details
16
Internal frequency values for different base frequencies
1.0000 MHz
1.6667 MHz
3.3333 MHz
5.0000 MHz
FREQ1
1.0000 MHz
1.6667 MHz
3.3333 MHz
5.0000 MHz
FREQ2
100.00 kHz
166.67 kHz
333.33 kHz
500.00 kHz
FREQ3
10.000 kHz
16.667 kHz
33.333 kHz
50.000 kHz
FREQ4
1.0000 kHz
1.6667 kHz
3.3333 kHz
5.0000 kHz
FREQ5
100.00 Hz
166.67 Hz
333.33 Hz
500.00 Hz
External sources
In addition to the five internal sources, the frequency source for the oscillator can be an input signal connected
to any of the five counter input pins (INP1 – INP5) or any of the five gate pins (GAT1 – GAT5). The input signal
can have a maximum frequency of 20 MHz on the counter input pins, and a maximum frequency of 7 MHz on
the gate pins.
The table below applies to all internal and external sources.
Oscillator sources
Source
Description
CTRINPUT1
Counter 1 input pin
CTRINPUT2
Counter 2 input pin
CTRINPUT3
Counter 3 input pin
CTRINPUT4
Counter 4 input pin
CTRINPUT5
Counter 5 input pin
GATE1
Counter 1 gate pin
GATE2
Counter 1 gate pin
GATE3
Counter 1 gate pin
GATE4
Counter 1 gate pin
GATE5
Counter 1 gate pin
FREQ1
Internal base frequency
FREQ2
Internal base frequency/10
FREQ3
Internal base frequency/100
FREQ4
Internal base frequency/1000
FREQ5
Internal base frequency/10,000
Divider (OSC divider)
The signal output from the OSC pin is the same frequency as the frequency source divided by a value from 1 to
16. For example, if you select a base frequency of 5.0000 MHz in InstaCal, and choose FREQ3 as the internal
frequency source (50.000 kHz from the Internal frequency values table above), and 8 as the oscillator divider,
the frequency of the signal at the OSC pin is (50.000 kHz / 8) = 6.2500 kHz.
Counter operation
Each of the five counters performs essentially the same function: their internal value either increments or
decrements on each rising or falling edge of their source signal. Since they are all 16-bit counters, they can
count up from 0 to 216-1 = 65,535, or down from 65,535 to 0. When counting up, 65,535 is considered to be the
Terminal Count (TC); when counting down, 0 is the TC. There are a variety of configuration options that can
be used to unlock the power of this basic functionality.

USB-4301 User's Guide Functional Details
17
Count source
Each counter on the device can count from any of the available sources. The sources for counting are the same
five internal sources and ten external sources listed in the Oscillator sources table (on page 16) with one
addition — each counter can also increment whenever the previous numbered counter reaches its TC (TC n-1).
For example, if you select TC n-1 as the counter source for Counter 2 Input (INP2), counter 2 increments or
decrements when counter 1 reaches TC. The previous numbered counter for counter 1 is counter 5. Note that
any of the 16 sources is available for any of the five counters. In other words, the signal source for counter 3 can
be Counter 5 Input or Counter 2 Gate, or FREQ4, and so on.
Gate control
The counter can be gated in several ways. Level gating typically allows the counter to count only while the gate
is active. Edge gating, on the other hand, typically starts the counting when an active gate edge is received.
Level gating configuration options are active high level Gate n, active low level Gate n, active high level
Gate n-1 and active high level Gate n+1, where Gate n is the Gate pin associated with the counter being
configured.
Edge gating configuration options are active high (rising edge) Gate n and active low (falling edge) Gate n.
The counter can be gated by the TC of the previous numbered counter. You can also disable gating.
Counting modes
Each of the five counters has two associated 16-bit registers which can be used to store count values — the
Load register and the Hold register.
The Load register is used to load the starting value for the counter.
The Hold register can be used to store a second counter value, or to save the current counter value.
Most applications only use the Load register. To start counting, configure the counter for the desired mode, and
then load the Load register with the starting value with which to start the counting operation.
Each counter can be configured to count up or to count down. The following sections explain the various
configuration options.
Reload
When the counter reaches TC it is always reloaded with a new value. This new value comes from one of two
sources:
Reload from the Load register. This mode can be used to generate constant frequency pulse trains.
Alternately load from the Load register and then the Hold register. This mode can be used for applications
that require delayed starts or to generate pulse trains with variable duty cycles.
Recycle
Each counter can be configured to count to TC and then stop counting, or to continue counting after reaching
TC. In either case, the counter is reloaded from the appropriate register when it reaches TC. However, if the
Recycle mode is set to stop counting at TC, and the reload mode is set to load from the Load and Hold registers,
it will count once to TC, reload from the Hold register, count again to TC, and then stop counting.
For example, if Counter 1 is configured as follows:
The Load 1 register contains the value 10,000
The Hold 1 register contains the value 5,000
Count down
Alternately load from the Load and Hold registers

USB-4301 User's Guide Functional Details
18
Not recycle
The counter will count from 10,000 to 0, and then start at 5,000 and count to 0, then stop. If you select an edge
gating option, and Recycle mode is active, the counter only resumes counting after TC when a new active gate
edge is received.
BCD/Binary mode
Most applications use the binary mode of counting. Binary mode causes the counter to always increment or
decrement by a value of 1. The counter can have a value from 0 to 65,535.
With binary mode, a 4-bit binary number is represented by the 16 decimal numbers 0 to 15: 0 = 0b0000, 1 =
0b0001,…, 9 = 0b1001, 10 = 0b1010,…, 15 = 0b1111. (0b is used to denote binary numbers). For the numbers
0-9, there are four binary bits to represent one decimal digit, and from 10-15, there are four binary bits to
represent two decimal digits.
However, in some applications, it is useful to maintain the four-bit-to-one-digit correspondence, so the numbers
0-9 remain the same, but 10-15 and up to 99 are represented by eight bits—four for each digit. The numbers
100-999 are represented by 12 bits, and 1000-9999 are represented by 16 bits. This makes it easy to decode long
binary numbers.
For example, 0b1001 0001 0000 1001 equals 9109 in BCD (Binary Coded Decimal) mode, and equals 37,129
in binary mode. In BCD mode, the counter can only contain values from 0 to 9999 instead of 0 to 65,535 as in
binary counting.
The "Special" gate
When you enable the Special gate option and specify gating, the gate can function as a hardware re-trigger of
the counting operation. When an active gate edge is received, the counter is reloaded from the Load register and
begins counting, even if the counter is already counting when the gate edge is received.
When you enable the Special gate option and disable gating, the Gate pin associated with the counter being
configured can select the reload source for the counter. This requires the counter be in Load and Hold reload
mode. If the gate pin is low, the counter is reloaded from the Load register. If the gate pin is high, the counter is
reloaded from the Hold register.
Output control
You can configure the output pin associated with a counter to behave in five ways:
Inactive with high impedance to ground.
Inactive with low impedance to ground.
Generate an active high pulse when the associated counter reaches TC.
Generate an active low pulse when the associated counter reaches TC.
Toggle its value every time the counter reaches TC.

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Example 1
Problem: The application generates an active low pulse every time a button1 is pressed. You need a simple
event counter to count button presses.
Solution: Any of the counters can be configured to do this fairly easily. Do the following:
1. Connect the input signal to the counter input pin, and select that input pin as the source for the counter.
2. Program the counter to:
oCount negative edge transitions
oCount up
oNo recycle
oCount in binary mode
oReload from the Load register
oDisable special gate
oNo gate control
oMake output control inactive
3. Load the Load register with a value of 0 to start counting.
Example 2
Problem: An external device generates an active high signal while a switch is depressed. The switch is
depressed for at most one second. You need to measure the time the switch is depressed with microsecond
accuracy.
Solution: Microsecond accuracy for one second requires counting to at most 1,000,000. However, each counter
can count only to 65,535. You can use some counter features to cascade two of the counters in order to count
higher. Configure Counter 1 and Counter 2 as follows:
Configure Counter 1:
1. Using InstaCal, configure the counter 1 source for 1 MHz. As shown in the "Internal frequency values"
table on page 16, an internal base frequency of 1.0000 MHz corresponds to FREQ1.
The internal base frequency of 1 MHz provides an ideal way to measure time to the microsecond, since
1 count at 1 MHz equals 1 microsecond.
2. The counter can count either up or down, so for this example set the counter to count up.
3. The counter should count only while the input signal from the switch is active. To do this, connect the input
signal to the gate 1 pin (GAT1), and configure the counter gate control for active high level Gate n.
4. Load the Counter 1 Load Register with a value of zero, since you want the counter to reach as high a count
as possible before reaching TC.
5. To cascade Counter 1 with Counter 2, turn Recycle mode on. This is done so Counter 1 continuously
counts to TC, then wraps around and starts counting at 0 again.
6. Set reload to always load from the Load register, since you want to restart at 0 after every TC.
7. Enable binary mode.
8. Set the Counter 1output to inactive; Counter 1 requires no special gating.
1 For more information about debouncing mechanical switches, refer to the "Low pass to de-bounce inputs" section
in MCC's Guide to Signal Connections . This document is available on our web site at
www.mccdaq.com/signals/signals.pdf.

USB-4301 User's Guide Functional Details
20
Configure Counter 2:
1. Set the count source for Counter 2 to be the (TC n-1). This causes Counter 2 to increment when Counter 1
reaches TC.
2. Load the Counter 2 Load Register 2 with a value of zero, since you want Counter 2 to start at 0 and count
up. Counter 2 requires no gating, no special gate, no reloading, and no recycling.
3. Enable binary mode.
When the button is depressed, Counter 1 will start counting from 0 to 65,535 over and over again. Every time
Counter 1 reaches 65,535, Counter 2 increments by 1 (starting from 0). When the button is released, Counter 1
stops counting. At that point, the count values can both be read.
The total time the button is pressed in µs is (Counter 2 counts * 65,536) + Counter 1 counts µs. If Counter 2 is
at 9 and Counter 1 is at 34,671, the total time is (9 * 65,536) + 34,671 = 624,495 µs = 0.624495 s.
Interrupt input pin (INT)
You can configure the interrupt input pin to perform the following tasks:
Generate an event notification that will be sent to the computer
Latch in the eight digital inputs.
When this option is active, the digital inputs always return the same value until a new active edge is
received on the interrupt pin. When the active edge is received, the current value is latched at the input
pins, and held until the next active edge.
Interrupt latency when latching inputs
There is a latency period between when an active interrupt edge occurs on the INT pin and when the action
triggered by that interrupt occurs. This latency can be as long as 100 µs, but typically varies from about 9 µs to
about 40 µs between interrupts.
Latch out a digital output value.
When this option is active, the digital outputs do not change state until a new active edge is received on the
interrupt pin. New values sent to the digital outputs are stored. The most recently received value is latched
out and held at the next active edge.
Save the current value of all five counters to their respective Hold registers. You can read the value of the
counter when the interrupt was received from the Hold registers.
For more information on the configuration options for your USB-4301, refer to the "USB-4300 Series" section
of the "Counter Boards" chapter in the Universal Library User's Guide. This document is available on our web
site at www.mccdaq.com/PDFmanuals/sm-ul-user-guide.pdf.