Installation Instructions

Hardware Installation
RVP8 User’s Manual
September 2005
2–36
The uplink signal, shown in Figure 2–5, is periodic at the radar pulse repetition frequency, and
conveys two distinct types of information to the IFD. The signal is normally low most of the
time (to minimize driver and termination power), but begins a transition sequence at the
beginning of each transmitted pulse.
Figure 2–5: Timing Diagram of the IFD Coax Uplink
12 345678910...
t
burst
t
s
t
s
t
s
t
s
t
s
The first part of each pulse sequence is a variable length “burst window” which is centered on
the transmitted pulse itself, and which has a duration t
burst
approximately 800ns greater than the
length of the current FIR matched filter. The burst window defines the interval of time during
which the IFD transmits digitized burst pulse samples, rather than digitized IF samples, on its
downlink. The exact placement and width of the burst window will depend on the trigger timing
and digital filter specifications that the user has chosen, usually via the Pb and Ps plotting setup
commands.
Following the burst window is a fixed-length sequence of 25 serial data bits which convey
information from the RVP8/Rx board. The first four data bits form a characteristic (0,1,1,0)
marker pattern. The first zero in this pattern effectively marks the end of the variable length
burst window, and the other three bits should be checked for added confidence that a valid bit
sequence is being received. Table 2–12 defines the interpretation of the serial data bits.
Table 2–12: Bit Assignments for the IFD Coax Uplink
Bit(s) Meaning
1–4 Marker Sequence (0,1,1,0). This fixed 4-bit sequence identifies the start
of a valid data sequence following the variable-length burst window.
5–20 16-bit multi-purpose data word, MSB is transmitted first (See below)
21 Reset Request. This bit will be set in just one transmitted sequence
whenever an RVP8 reset occurs.
22 If set, then interpret the 16-bit data word as 4-bits of command and
12-bits of data, rather than as a single 16-bit quantity (See below)
23–24 Diagnostic select bits. These are used by the RVP8 power-up diagnostic
routines; they will both be zero during normal operation.
25 Green LED Request; 0=Off, 1=On. The state of this bit normally
follows the “Downlink Detect” LED on the RVP8/Rx board.