For each pulse width there is a corresponding minimum trigger PRT permitted. This bound
limits the transmitter duty cycle to a safe value under all conditions. PWINFO sets up these
minimum PRTs using words 2 ... 5 following the command. The maximum frequency of the
internal trigger generator is then constrained at each pulse width to the indicated rate. This
protection applies at all times, that is, during noise sampling, during ray processing, and
during the standby time between rays. The default PRT bounds are 2000, 1000, 750, and
500 Hertz (Inputs of 3000, 6000, 8000, and 12000). If your radar does not use all of the
pulse width codes, it is still a good idea to set the unused PRT limits to reasonable values.
This way protection is still provided if that SETPWF accidentally selects one of the unused
states. If the internal trigger generator is not being used, then the PRT limits no longer
aect
the trigger rate and transmitter protection becomes the responsibility of the user hardware.
You can turn o the pulse/bandwidth mechanism by setting the bit patterns and PRT
limits all to the same value.
The PWINFO command can be disabled (for transmitter safety), so that PRT limits cannot
accidentally be changed by the host computer. When this is done RVP900 still reads the
five
input words, but no changes are made to the pulse width and PRT information. The
command I/O behaves the same way, whether enabled or disabled.
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| |UpperPW| | 0 1 1 1 1 | Command
|-----------------------|---|---|------------|-------------------|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Bits for PW 3 | Bits for PW 2 | Bits for PW 1 | Bits for PW 0 | Input 1
|---------------|---------------|----------------|---------------|
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
---------------------------------------------------------------
| | | | | | | | | | | | | | | | |
| Min Trig Period (0.16667usec Increments) for Pulse Width 0 | Input 2
|----------------------------------------------------------------|
Chapter 8 – Host Computer Commands
295
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