User's Manual Part 2

Host Computer Commands
RVP8 User’s Manual
May 2003
6–35
code. This is done using word #1 following the command, which contains four codes packed
into one 16-bit word. The power-up default is to drive output line N low for a code of N,
keeping all other lines high (Input of 7BDE Hex). The flexibility in defining the output bits
usually makes the radar hardware connections very simple. For example, if pulsewidth selection
relied on choosing one of four relays, then each PWBWn line could serve directly as a relay
driver using the default pattern.
For each pulse width there is a corresponding minimum trigger PRT permitted. This bound is
intended to limit the transmitter duty cycle to a safe value under all conditions. PWINFO sets up
these minimum PRT’s using words 2 through 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, i.e., 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 four
pulse width codes, it is still a good idea to set the unused PRT limits to reasonable values. This
way protection is still provided in the event that SETPWF accidently selects one of the unused
states. If the internal trigger generator is not being used, then the PRT limits no longer affect the
actual trigger rate and transmitter protection becomes the responsibility of the the user hardware.
Finally, note that the entire pulse/bandwidth mechanism can be effectively turned off by setting
the four bit patterns and the four PRT limits all to the same value.
The PWINFO command can be disabled (for transmitter safety), so that PRT limits cannot
accidently be changed by the host computer. When this is one, the RVP8 still reads the five
input words, but no changes are made to the pulse width and PRT information. Thus, 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
| | | | | | | | | | | | | | | | |
| | 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
|_______________________________________________________________|
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 1 | Input 3
|_______________________________________________________________|
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 2 | Input 4
|_______________________________________________________________|
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 3 | Input 5
|_______________________________________________________________|