Racal Instruments 3151 User Manual page 59

3151 And 3151A User Manual
Memory
Model 3151/3151A. In shared memory mode, the Model
3151/3151A'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 3151/3151A, control
is returned to the instrument.
In shared memory mode, the Model 3151/3151A 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 3151/3151A 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.
The query:
SMEMory:MODE?
queries the shared memory mode and returns READ or WRITE.
The command:.
SMEMory:STATe {OFF | ON}
places the Model 3151/3151A in the shared memory state when ON
is selected. After this, the instrument cannot accept normal
commands. Data must be sent to the generator using shared
memory access. Normal command mode is resumed when the
SMEMory:STATe is changed to OFF.
The query:
SMEMory:STATe?
queries the shared memory state and returns "0" (OFF) or "1" (ON).
The following sequence should be used for shared memory
Using The Instrument 3-29