Programming instructions

Downloading and Using Files
Downloads Directly into Pattern RAM (PRAM)
Chapter 4 183
Downloads Directly into Pattern RAM (PRAM)
Typically, the signal generator’s firmware generates the required data and framing structure
and loads this data into Pattern RAM (PRAM). The data is read by the baseband generator,
which in turn is input to the IQ modulator. The signal generator can also accept data
downloads directly into PRAM from a computer. Programs such as MetLab

or MathCad

can generate data which can be downloaded directly into PRAM in either a list format or a
block format.
Direct downloads to PRAM allow you complete control over bursting which is especially
helpful for designing experimental or proprietary framing schemes.
This section contains information that will help you transfer user-generated data from a
system controller to the signal generator’s PRAM. It explains how to download data directly
into PRAM and modulate the carrier signal with the data.
The signal generator’s baseband generator assembly builds modulation schemes by reading
data stored in PRAM and constructing framing protocols according to the data patterns
present. PRAM data can be manipulated (types of protocols changed, standard protocols
modified or customized, etc.) by the front panel interface or by remote-command interface.
NOTE Because there is no parsing involved, block data format downloads are
significantly faster than list format downloads.
Data Limitations
Total (data bits plus control bits) download size limitations are 8 Mbytes or 32 Mbytes with
Option 002. Each sample for PRAM uses 4 bytes of data.
A data pattern file containing 8 Mbits of modulation data must contain another 56 Mbits of
control information. A file of this size requires 8 Mbytes of memory; the largest amount of
modulation data for a waveform in the signal generator without Option 002.
Data Volatility
The signal generator provides two data storage areas: volatile waveform memory (WFM1) and
non-volatile memory (NVWFM). Data stored in volatile waveform memory cannot be
recovered if it is overwritten or if the power is cycled. Data stored in non-volatile memory,
however, remains until you delete the file. The Option 005 signal generator’s hard disk
provides 6 Gsamples of non-volatile storage. Signal generators without Option 005 provide
3 Msamples of non-volatile storage.