Racal Instruments 3152, User Manual

Page: 49 / 123

Using The Instrument 3-24
NOTE
T h e M o d e l 3 1 5 2
o p e r a t e s i n i n t e r l a c e d
mode where two memory cells generate one byte of data.
Segment size can be programmed in even-numbers only and
the generator can accept binary blocks of data that are
multiples of 4 only. For example, 2000 bytes will be an
acceptable binary block. 2002 is not a multiple of 4, therefore,
the generator will automatically adjust the size to 1002 points
and generate an error message.
Reversing Byte Order Binary data is sent to the Model 3152 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 3152. In shared memory mode, the Model 3152'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 3152, control is returned to the instrument.
In shared memory mode, the Model 3152’s memory acts similar to
Direct Memory Access (DMA). The instrument has to be told when
to receive data, send data, surrender control or gain control. The
Model 3152 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.
To write to or read from a segment, the user must first define the
segment using the command TRACe:DEFine. The trace must then
be selected using the command TRACe:SELect. Refer to Loading
Arbitrary Waveforms for more information.
The command:
SMEMory:MODE {READ | WRITe}
sets the instrument to receive data from (WRITE) or send data
(READ) to the VXIbus.