Figure 18-2 Ieee-754 Single Precision Data Format (32 Data Bits) - Keithley SourceMeter 2400 User Manual

18-50 SCPI Command Reference
IEEE-754 single precision format
REAL,32, or SREal will select the binary IEEE-754 single precision
data format.
data element. For example, if three valid elements are specified, the data
string for each reading conversion is made up of three 4-byte data
blocks. Note that the data string for each reading conversion is preceded
by a 2-byte header that is the binary equivalent of an ASCII # sign and 0.
Figure 18-2
the end of each data string.
Figure 18-2
IEEE-754 single precision data format (32 data bits)
Header Byte 1
# 0
7
s e
s = sign bit (0 = positive, 1 = negative)
e = exponent bits (8)
f = fraction bits (23)
Normal byte order shown. For swapped byte order, bytes sent
in reverse order: Header, Byte 4, Byte 3, Byte 2, Byte 1.
The header and terminator are sent only once for each READ?.
During binary transfers, never un-talk the SourceMeter until after the
data is read (input) to the computer. Also, to avoid erratic operation, the
readings of the data string (and terminator) should be acquired in one
piece. The header (#0) can be read separately before the rest of the
string.
The number of bytes to be transferred can be calculated as follows:
Bytes=2+(Rdgs × 4) + 1
where 2 is the number of bytes for the header (#0).
For example, assume the SourceMeter is configured to perform 10
source-measure operations and send the 10 current measurements to the
computer using the binary format.
Bytes = 2 + (10 x 4) + 1
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2400 Series SourceMeter
Figure 18-2 shows the normal byte order format for each
does not show the byte for the terminator that is attached to
Byte 2 Byte 3
0 7 0 7 0 7
f
Rdgs is the product of the number of selected data elements, arm
count, and trigger count.
4 is the number of bytes for each reading.
1 is the byte for the terminator.
= 43
®
User's Manual
Byte 4
0