Keithley KPCI-3110, Руководство пользователя

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2-20 Functional Description KPCI-3110 and KPCI-3116 User’s Manual
Waveform generation
Use waveform generation mode if you want to output waveforms repetitively.
Before this process can begin, the host computer must transfer the entire waveform pattern to
output to the DACs from computer memory into the Output FIFO on the board.
For the KPCI-3110 and KPCI-3116 boards, if you are using a single DAC, the waveform pattern
can range from 2 to 4,096 samples. If you are using two DACs, the waveform pattern can range
from 2 to 2,048 samples.
When it detects a trigger, the board cycles through the analog output channel-gain list, convert-
ing and outputting the specified waveform for the specified DACs. When the Output FIFO emp-
ties, the board issues a retransmit pulse to the Output FIFO. This allows the board to output the
same pattern continuously to the DACs without having to reload the Output FIFOs. Refer to
page 2-20 for more information on buffers.
The conversion rate is determined by the frequency of the D/A output clock. For KPCI-3110
boards, the maximum throughput rate in this mode is 500kHz (500 kSamples/s) in 100mV steps.
For the KPCI-3116 boards, the maximum throughput rate in this mode is 200kHz
(200 kSamples/s) in 100mV steps. Refer to
page 2-17 for more information on the D/A output
clock.
To select waveform generation mode, refer to the “Using DriverLinx with your hardware:
KPCI-3100 Series” manual.
Data format and transfer
Data from the host computer must use offset binary data encoding for analog output signals.
DriverLINX converts this “native format” to a hardware-independent format so that applications
can use the numeric operations that are intrinsic to most high-level languages. A DriverLINX
Service Request may be used for several types of data conversion (such as VOLTS2CODE con-
version that converts analog voltage to D/A code). Because the data values depend on the
selected gain at the time of the data transfer, you should use DriverLINX to convert the data, as
it takes the gain properties of the Service Request into account.
NOTE Refer to the DriverLINX Analog I/O Programming Guide and the
“Using DriverlINX with your Hardware” manuals furnished with
DriverLINX.
Error conditions
KPCI-3110 and KPCI-3116 boards can report an Output FIFO Underflow error to the host com-
puter. This error indicates that the analog output data was not being transferred fast enough
across the PCI bus from the host computer to the Output FIFO on the board.
If the D/A output clock occurs while the Output FIFO is empty, an error is not reported since the
most likely cause is that the host computer has no more data to output. In this case, the last value
received from the host computer is output by the specified DACs continuously until the board is
powered down or new data becomes available. If, however, the host does an additional write to
the Output FIFO (after the D/A output clock occurred while the Output FIFO was empty), the
data is written to the DACs and the Output FIFO Underflow error is reported. This error has no
effect on board operation; the host computer can clear this error.