Stanford Research Systems SR844 User Manual page 129

When using the GPIB interface, <EOI> is sent with the final byte. The points must
be read using a binary transfer (see your GPIB interface card software manual).
Make sure that the software is configured to not terminate upon receipt of a <CR>
or <LF>.
Important!
•
•
When using the RS232 interface the points must be read as binary bytes (no
checking for linefeeds, carriage returns or other control characters). Most serial
interface drivers are designed for ASCII text only and will not work here. In
addition, the data transfer does not pause between bytes. The receiving interface
must always be ready to receive the next byte. In general, using binary transfers on
the RS232 interface is not recommended.
TRCL? ch,j,k
The TRCL? command queries the points stored in the Display ch buffer. The
values are returned in non-normalized floating point format in the units of the
trace. There are four bytes per point. Multiple points are not separated by any
delimiter. The bytes cannot be read directly into a floating point array.
Each point consists of four bytes. Byte 0 is the LSB and is transmitted first. Byte 3
is the MSB. The format is illustrated below.
The mantissa is a signed 16 bit integer (–32768 to +32767). The exponent is a
signed integer whose value ranges from 0 to 248 (thus byte 3 is always zero). The
value of the data point is
The data within the SR844 is stored in this format, so data transfers using this
format is faster than IEEE floating point format. If transfer speed is important, then
the TRCL? command should be used.
The parameter ch selects the display buffer (1 or 2) and is required. Points are
read from the buffer starting at bin j (j
read a single point, set k=1. Both j and k are required. If j+k exceeds the
number of stored points (as returned by the SPTS? query), then an error occurs.
When using the GPIB interface, <EOI> is sent with the final byte. The points must
be read using a binary transfer (see your GPIB interface card software manual).
Make sure that the software is configured to not terminate upon receipt of a <CR>
or <LF>.
If data storage is set to Loop mode, be sure to pause data storage before
reading any data. This is because the points are indexed relative to the oldest
point, which is continually changing.
Do not query the Interface Ready status bit after sending the TRCB?
command. This bit will not be set until the transfer is complete.
16 bits
0 exp
byte3 byte2
value = mantissa × 2
Data Transfer 4-27
16 bits
mantissa
byte1 byte0
[exponent – 124]
≥
0). A total of k bins are read (k
SR844 RF Lock-In Amplifier
≥
1). To