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October 1, 1995
Changing Baud Rate on the DDF4003 or DDF5003
A Technical Application Note from Doppler Systems, Inc.
1. Introduction
The baud rate of the DDF4003 and DDF5003 is determined by the clock frequency input to the serial board, DDF4104. The change must be made on the logic board, DDF4102. It is possible to increase the baud rate from 300 to 600, 1200 or 2400 baud with a single cut and jumper wire.
2. Procedure
Remove the main logic board from
the case noting the location and orientation of the various
connecting cables.
The trace which is to be cut is located on the top (component) side of the board near U2. See the figure to locate the trace. Note that there are two traces that run from U2 to the inside of U5. Using a sharp knife, cut the trace indicated.
On the solder side of the board, locate U2 and U5. Connect the pins shown in the following table using a length of fine gage wire. Number 26 wire wrap wire works well. Solder both ends.
Reassemble the unit paying particular attention that you get the connecting cables properly reattached.
| Baud Rate | Connect U2, pin 11 to: |
| 300 | U18, pin 5 |
| 600 | U18, pin 4 |
| 1200 | U18, pin 3 |
| 2400 | U18, pin 2 |