Stanford Research Systems DS345, Manual

Page: 58 / 139

Programming Commands
3-8
Arbitrary PM:
Each arbitrary PM point is a 32 bit integer value. This value is the phase shift
to be made relative to the current phase. The values may range from -180°
to +180°. The 32 bit value is calculated from the formula: value = 2 31 *
(phase shift/180°). Negative values are expected in 2's complement format
(bit 31 is the sign bit). Thus, the i data points form a list of i phase shifts to
be executed. The i data values should be followed by a 32-bit checksum-
simply the 32-bit sum of the data values. Thus, a total of i+1 32-bit values
will be sent. When modulation is enabled each modulation point takes
N*0.5
µ
s to execute, where N is the arbitrary modulation rate divider (see the
AMRT command). The MODULATION OUTPUT will output the modulation
waveform when modulation is enabled, with 0 V corresponding to the mini-
mum phase shift and 5.0 V corresponding to the maximum phase shift in the
modulation pattern.
LDWF? i,j
The LDWF? query allows downloading arbitrary waveforms in either point
(i=0) or vector (i=1) format. In point mode j is the number of points in the
waveform (16300 maximum), while in vector format j is the number of vertic-
es (6144 maximum). The data is sent as 16 bit binary data words. The data
must be followed by a 16 bit checksum to ensure data integrity. The check-
sum is the 16bit sum of the data words that have been sent. If the checksum
sent does not match the one calculated by the DS345 an error will be gener-
ated. If the data sent is valid and the DS345's function is set to ARB the
waveform will automatically be output. Otherwise, the function must be set to
ARB to output the downloaded waveform. To load a waveform follow these
steps:
1) Send the query LDWF? i,j where i and j are appropriate for the waveform
type and number of points desired.
2) Wait until the DS345 returns "1" indicating that it is ready to receive data.
3) Send the waveform data (discussed below). There should be j data points
sent.
4) Send the 16 bit checksum (the sum of j data points).
The waveform data is send as 16 bit
binary
data. In point mode each data
point consists of a 16 bit amplitude word. Each value should be in the range
-2047. In vector mode each data point consists of a 16 bit x vertex
word and a 16 bit y vertex word (for a total of 2*j 16 bit words). Each x value
must be in the range 0 to 16299 and must be greater than or equal to the val-
ue of the previous x value. Each y value must be in the range -2047 to
+2047. The checksum is the 16 bit sum of the j words sent in point mode or
the 2*j words sent in vector mode.