Programming instructions

Downloading and Using Files
User File Data Downloads
Chapter 4170
User Files as Data Source for Framed Transmission
Specifying a user file as the data source for a framed transmission provides you with an easy
method to multiplex real data into internally generated TDMA framing. The user file will fill
the data fields of the active timeslot in the first frame, and continue to fill the same timeslot of
successive frames as long as there is more data in the file. This functionality allows a
communications system designer to download and modulate proprietary data sequences,
specific PN sequences, or simulate multiframe transmission, such as those specified by some
mobile communications protocols. As the example in the following figure shows, a GSM
multiframe transmission requires 26 frames for speech.
Figure 4-1 GSM Multiframe Transmission
When a user file is selected as the data source for a framed transmission, the signal
generator’s firmware loads PRAM with the framing protocol of the active TDMA format. For
all addresses corresponding to active (on) timeslots, burst bits are set to 1 and data bits are
set with the contents of the user file for the data fields of the timeslot. Other bits are set
according to the configuration selected. For inactive (off) timeslots, burst control bits are set to
0, and data is “unspecified.” Pattern reset is set to 1 for the last byte in PRAM, causing the
pattern to repeat after the last byte is read.