Racal Instruments 3162A/B, User Manual

Page: 67 / 144

User Manual 3162A/B
Using The Instrument 3-33
/* Download 24 points */
ri3162B_load_arb_data (vi, 1, data_pts, 24);
}
The above program uses the VISA I/O library and the LABWindows/CVI driver.
Reversing Byte
Order
Binary data is sent to the Model 3162B in byte-high byte-low order. This order
can be reversed using the following command:
FORMat:BORDer {NORMal | SWAPped}
The default is NORM. This command is useful only for binary block transfers.
The query:
FORMat:BORDer?
queries the byte order configuration and returns "NORM" or "SWAP".
Using Shared
Memory
Shared memory transfer is the fastest way to get waveforms into the Model
3162B. In shared memory mode, the Model 3162B's CPU disconnects from the
waveform memory and passes access to the VXIbus. The internal data bus is
connected directly to the VXIbus, and data is downloaded into the memory in
binary blocks using A24 memory space. Byte and bit order are the same as
with the Arbitrary Block transfers as shown in Figures 3-1 and 3-2. After the
data is loaded into the Model 3162B, control is returned to the instrument.
In shared memory mode, the Model 3162B s memory acts like Direct Memory
Access (DMA). The instrument must be told when to receive data, send data,
surrender control or gain control. The Model 3162B has an auto-increment
address counter. The Slot 0 Controller need only select the base address for
both write and read cycles. Shared Memory commands are explained below.
The maximum block of shared memory that can be downloaded in a single
transfer is 2Meg (2097152) words. If segments greater than 2Meg are needed,
then multiple segments must first be defined. Then loaded with up to 2Meg of
data, and then re-defined as a single segment of the desired size. For the
example of a 3Meg segment, segments 1 and 2 can be defined as 2Meg and
1Meg, respectively. Two downloads are then required of 2Meg and 1Meg to
these segments. Then segment 1 is redefined as 3Meg and the process is
complete.
To write to or read from a segment, the user must first define the segment
using the TRACe:DEFine command. The trace must then be selected using
the TRACe:SELect command. Refer to Loading Arbitrary Waveforms (Page 3-
31) for more information.
The command:
Revised 5/7/01