LeCroy LW110 User Manual page 128

Transfer of definite length arbitrary block data must terminate with the EOI bit set. This way, carriage-return
(CR – 0dH) and line feed (LF – 0aH) characters can be used as waveform data points and will not cause
unexpected termination of the arbitrary block data.
•
<binary_block>
The waveform data is made of 16-bit words however, the GPIB link has 8 data bas lines and accepts 8-bit
words only. Therefore, the data has to be prepared as 16-bit words and rearranged as two 8-bit words
before it can be used by the LW120 as waveform data points. The following description shows you how to
prepare the data for downloading to the LW120. There are a number of points you should be aware of
before you start preparing the data:
1. Each channel has its own waveform memory. Therefore, make sure you selected the correct active
channel before you download data to the generator
2. Waveform data points have 14-bit values
3. Data point range is 0 to 16,383 decimal
4. Data point 0 to data point 16,383 corresponds to full-scale amplitude setting. For example, if your
amplitude setting is 5V
corresponding level in waveform points is decimal 0 (0x0000) for –2.5V and decimal 16,393 (0x3FFF)
for 2.5V. Similarly, the 0V point will correspond to decimal 8191 (0x1FFF)
5. The two most significant bits – D14 and D15 are control bits and are not available for normal
programming. They must be set to "0" at all times except during DMA download where the last word is
sent with D15 set to "1". Information on this special mode is given later in this chapter
Figure 4-2 shows how to initially prepare the 16-bit word for a waveform data point. Note that there are 14
bits used for data representation. The other two bits are used for control purpose and must be set to "0".
Also note that the LW120 can not accept formats as shown in Figure 4-2; Data has to be further
manipulated to a final format that the instrument can accept and process as waveform point.
MSB
D15 D14
Figure 4-3 shows the same 16-bit word as in Figure 4-2, except the high and low bytes are swapped. This is
the correct format that the LW120 expects as waveform point data. The first byte to be sent to the generator
is the low-byte and then high-byte.
Remote Programming Reference 4-46
Represents waveform data.
, your generator will output waveforms from –2.5V to +2.5V. The
pk-pk
high-byte
D13 D12 D11 D10 D9
14-bit binary value (0 to 16383 decimal)
2 control bits. Must be set to 0, initially
Figure 4-2
. 16-bit Initial Waveform Data Point Representation
low-byte
D8 D7 D6 D5 D4
User Manual LW120
LSB
D3 D2 D1 D0