3156B User Manual
Using the Instrument 3-24
Racal Instrument © 2005
The next step is to transfer data to the active segment. Use the
following function call:
ri3156B_load_arb_data
()
This function call has three variables:
Segment number – defines the specific segment where you intend
to load the data
Data points array – provides an array of data points, or waveform
coordinates that will be sampled by the
instrument to generate the required waveform.
The data array is constructed from 16-bit words,
sent in words and is placed in the buffer is two
bytes, high byte first. The order of the bytes can
be changed, if required by swapping the high
and low bytes, and
Number of points – which define and must match the number of
waveform coordinate in the above array
Using the 12-bit
Download mode
Data for the data point array is stored in 16 bit words. In cases where
only 12 bit data arrays are available, for example, waveform file that
were used previously on other 12-bit waveform generators, the 3156B
can be adjusted to accept 12-bit data. Regardless, the data is stored
in 16 bit words and therefore, the 12-bit data must be multiplied by 8
so that the MSB bit is shifted 4 places to the left. The data format can
be switched by using the following function call:
ri3156B_set_wave_format
()
Reversing Byte
Order
Data is placed in the data points array in byte-high byte-low order.
This order can be reversed using the following function call
ri3156B_set_byte_order
()
The default is high-byte, low-byte
Changing the
Sample Clock
Frequency
Users should be careful not to confuse waveform frequency with
sample clock frequency. The waveform frequency parameter is valid
for standard waveforms only and controls waveform frequency at the
output connector. On the other hand, the sample clock frequency
parameter is valid for arbitrary and sequenced waveforms only and
defines the frequency at which the generator clocks data points.