buffered event counting, and continuous buffered pulse train
measurements. The NI 660x counter/timer devices are readily
integrated into measurement systems that require synchronization
across multiple hardware devices because they are equipped with the
National Instruments PXI trigger bus or the RTSI bus. See the
counter/timer tutorial on page 789 for more information.
In addition to counter/timer functionality, the NI 660x products
include TTL/CMOS-compatible digital I/O ports that are bit
configurable for input or output.
Counter/Timer Size or Number of Bits
The counter size or number of bits indicates how high a counter can
count. For example, a 32-bit counter can count up to 2
32
-1 or
4,294,967,295 before it rolls over. A high number of bits is beneficial
in cases such as pulse width measurements where a wide dynamic
range is required. For example, if you measure pulse widths with a
12.5 ns resolution (80 MHz timebase) using a counter/timer with
32 bits, you can measure pulse widths up to 53 s [(2
32
-1) x 12.5 ns)]
with 12.5 ns resolution.
Data Acquisition and
Signal Conditioning
Maximum Source Frequency
Counter/Timer Considerations
Number of Counter/Timers
The counter/timer is a basic unit of hardware functionality on a
measurement device. The more counter/timers there are on a device,
the more counting/timing operations that device can simultaneously
perform. The number of DMA channels determines how many
buffered, high-speed operations can be simultaneously performed.
See page 393 for more information.
Maximum source frequency represents the speed of the fastest signal
the counter can count. If you use a higher source frequency, you can
achieve higher resolution. For example, an 80 MHz counter can
count pulses that are 12.5 ns (
1
⁄
80 x 10
) apart. You can use prescalers to
increase the maximum source frequency for event counting and
frequency measurement.
6
Family
NI 6601
NI 6602
NI 6608
1
Max
2
DMA
Bus
PCI
PCI
PXI
PXI
Counter/
Timers
4
8
8
Size
32 bits
32 bits
32 bits
Max Source
Frequency
20 MHz
1
80 MHz
1
80 MHz
1
Compatibility
5 V TTL/CMOS
5 V TTL/CMOS
5 V TTL/CMOS
Digital I/O
Up to 32
Up to 32
Up to 32
Pulse
Generation
✓
✓
✓
Buffered
Operations
✓
✓
✓
Debouncing/
Glitch
Oscillator
Removal
Stability
✓
50 ppm
✓
50 ppm
✓
75 ppb
GPS
Synchr.
–
–
✓
Buffered Operations
2
DMA
Interrupt
1
3
3
5
3
5
Page
388
388
388
Source Frequency with prescalers is 60 MHz for the NI 6601 and 125 MHz for the NI 6602 and NI 6608. These frequencies are dependent on drive strength of input signal and cable length. Consider these speeds to be the maximum.
transfers have higher throughput than interrupt transfers. See page 393 for detailed specifications.
NI 660x devices are timing and digital I/O (DIO) modules for PCI
and PXI. They offer up to eight 32-bit counter/timers and up to
32 lines of 5 V TTL/CMOS-compatible digital I/O. You can perform
a wide variety of buffered measurements or other counter/timer
tasks with NI 660x devices, including position or quadrature encoder
measurement, event counting, period measurement, pulse-width
measurement, frequency measurement, pulse generation, and pulse-
train generation.
Features
Counter/Timers
The NI 660x devices are equipped with the NI-TIO ASIC, a
National Instruments counter and digital I/O ASIC for advanced
timing and counting applications. Each NI 6602 and NI 6608 device
features two NI-TIO ASICs to provide a total of eight counter/timers.
Counter/
Timers
4
8
8
Max Source
Frequency
20 MHz
1
80 MHz
1
80 MHz
1
The PCI-6601 board features one NI-TIO ASIC for a total of four
counter/timers. The counters are software-compatible with those
found on E Series multifunction DAQ devices, but NI 660x devices
offer additional capabilities.
Each counter has a gate, up/down, and source signal, which can be
controlled by external or internal signals. Each counter has one
output that can be routed externally or to other counters on the
device. 20 MHz and 100 kHz timebases are available on each device
for use with each counter/timer. In addition, an 80 MHz timebase is
available on the NI 6602 and NI 6608 devices. A hardware trigger can
be used to start multiple counters simultaneously. See Table 1 for
more information.
Family
NI 6601
NI 6602
NI 6608
1
Max
Bus
PCI
PCI
PXI
PXI
Size
32 bits
32 bits
32 bits
Compatibility
5 V TTL/CMOS
5 V TTL/CMOS
5 V TTL/CMOS
Digital I/O
Up to 32
Up to 32
Up to 32
Pulse
Generation
✓
✓
✓
Buffered
Operations
✓
✓
✓
Debouncing/
Glitch
Oscillator
Removal Stability
✓
50 ppm
✓
50 ppm
✓
75 ppb
GPS
Synchr.
–
–
✓
Buffered Operations
2
DMA
Interrupt
1
3
3
5
3
5
Source Frequency with prescalers is 60 MHz for the NI 6601 and 125 MHz for the NI 6602 and NI 6608. These frequencies are dependent on drive strength of input signal and cable length. Consider these speeds to be the maximum.
2
DMA transfers
have higher throughput than interrupt transfers.
Table 1. NI 660x Products Specifications Summary (See page 393 for detailed specifications.)
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