Chapter 4 183
Downloading and Using Files
Downloading Directly into Pattern RAM (PRAM)
Data Requirements and Limitations
1. Data format:
List Format: Because list format downloads are parsed before they are loaded into PRAM, data must be
8-bit, unsigned integers, from 0 to 255.
Block Format: Because the baseband generator reads binary data from the data generator, data must be in
binary form.
2. Total (data bits plus control bits) download size limitations are 32 megabytes with Option 002 and 64
megabytes with Option 602. Each sample for PRAM uses 4 bytes of data.
A data pattern file containing 8 megabits of modulation data must contain another 56 megabits of control
information. A file of this size requires 8 megabytes of memory.
3. For every bit of modulation data (bit 0), you must provide 7 bits of control information (bits 1-7).
The signal generator processes data in 8-bit bytes. Each byte contains 1 bit of “data field” information,
and seven bits of control information associated with the data field bit. See the following table for the
required data and control bits.
Bit Function Value Comments
0 Data 0/1 The data to be modulated; “unspecified” when burst (bit 2) = 0.
1 Reserved 0 Always 0.
2 Burst 0/1 Set to 1 = RF on.
Set to 0 = RF off.
For non-bursted, non-TDMA systems, this bit is set to 1 for all memory locations,
leaving RF output on continuously. For framed data, this bit is set to 1 for on timeslots
and 0 for off timeslots
3 Reserved 0 Always 0.
4 Reserved 1 Always 1.
5 Reserved 0 Always 0.
6 Event 1 Output 0/1 Set to 1 = a level transition at the EVENT 1 BNC connector.
Use examples: as a marker output to trigger external hardware when data pattern
restarts; toggling in alternate addresses to create a data-synchronous pulse train.
7 Pattern Reset 0/1 Set to 0 = continue to next sequential memory address.
Set to 1 = end of memory and restart memory playback.
Set to 0 for all bytes except last address of PRAM, where 1 restarts pattern.
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