User`s guide

PCI-2513 User's Guide Functional Details

Digital input channel sampling is not done during the "dead time" of the scan period where no analog sampling

is being done either.

The ability to scan digital and counter channels along with analog channels provides for a more deterministic

collection of data.

Bus mastering DMA

The PCI-2513 supports bus mastering DMA. With multiple DMA channels, analog, digital, and counter input

data, as well as digital output data, can flow between the PC and the PCI-2513 without consuming valuable

CPU time. The driver supplied with the PCI-2513 automatically uses bus mastering DMA to efficiently conduct

I/O from the PC to the PCI-2513.

Analog input

The PCI-2513 has a 16-bit, 1-MHz A/D coupled with 16 single-ended or eight differential analog inputs. Seven

software programmable ranges provide inputs from ±10 V to ±100 mV full scale.

Analog input scanning

The PCI-2513 has several scanning modes to address various applications. You can load the 512-location scan

buffer with any combination of analog input channels. All analog input channels in the scan buffer are measured

sequentially at 1 µs per channel by default.

For example, in the fastest mode, with 1 µs settling time for the acquisition of each channel, a single analog

channel can be scanned continuously at 1 MS/s; two analog channels can be scanned at 500 kS/s each; 16

analog input channels can be scanned at 62.5 kS/s.

Settling time

For most applications, leave the settling time at its default of 1 µs.

However, if you are scanning multiple channels, and one or more channels are connected to a high-impedance

source, you may get better results by increasing the settling time. Remember that increasing the settling reduces

the maximum acquisition rate.

You can set the settling time to 1 µs, 5 µs, 10 µs, or 1 ms.

Example: Analog channel scanning of voltage inputs

Figure 4 shows a simple acquisition. The scan is programmed pre-acquisition and is made up of six analog

channels (Ch0, Ch1, Ch3, Ch4, Ch6, Ch7). Each of these analog channels can have a different gain. The

acquisition is triggered and the samples stream to the PC via DMA. Using the default settling time, each analog

channel requires one microsecond of scan time—therefore the scan period can be no shorter than 6 µs for this

example. The scan period can be made much longer than 6 µs—up to 1 second. The maximum scan frequency

is 1 divided by 6 µs, or 166,666 Hz.