User's Manual

Host Computer Commands
RVP8 User’s Manual
March 2006
6–1
6. Host Computer Commands
This chapter describes the digital commands that the host computer must use to set up and
control the RVP8 processor for recording data. Each command is described in detailed in a
separate section of this chapter. Note that a command mnemonic, or shorthand reference name,
is given in each section heading. These names are frequently used to refer to particular
commands.
The write–up for each command includes a description of what the command does and a
pictorial layout of the bits in the 16-bit command word. Commands consist of an initial
command word containing an opcode in the low five bits. If additional arguments are required,
they are listed as “Input 1”, “Input 2”, etc. Finally, if the command produces output, those
words are listed as “Output 1”, “Output 2”, etc. Often each word is broken down into several
independent fields, each consisting of one or more bits. In such cases, the pictorial layouts show
the placement of the bit fields within the word, and each field is described individually. All data
transferred to or from the RVP8 are in the form of 16-bit words.
Before attempting to program the RVP8, it is a good idea to at least skim through the
descriptions of every command. The instruction set has been designed to be as concise and
orthogonal as possible. User programs should always execute the IOTEST command on
power-up to ensure that the interface connections are all intact. The diagnostic result registers
from GPARM should also be checked initially to verify that the RVP8 passed all internal checks.
Since all internal RVP8 tables and parameters are set to reasonable values on power-up, it is
conceivable that PROC commands could be issued immediately to acquire and process radar
data. More realistically, however, the default information is first modified to meet the users
needs.
To set up for data acquisition and processing the following sequence of commands might be
executed. Trigger and pulse width are first established using the SETPWF commands. Range
bin placement and processor options are then chosen using LRMSK, and SOPRM, and receiver
noise samples are taken with SNOISE. The noise levels are not automatically sampled on
power-up, so SNOISE must be issued at least once by the user. LFILT is executed if clutter
filters are needed. If data rays are to be synchronized with antenna motion, then LSYNC is used
to specify a table of antenna angles. After all setups are complete, PROC commands are issued
to actually collect, process, and output the data. Errors detected during the execution of
commands are noted by the RVP8 and can be monitored using GPARM.
The RVP8 contains a 4096-word first-in-first-out (FIFO) buffer through which all output data
flow. This buffer is included to simplify the requirements of the user’s interface hardware. The
FIFO holds each sequential word generated by the RVP8 until such time as the user is ready to
accept it. Thus, when reading from the processor, it is permissible to fall behind by as many as
4096 words before any slowdown in performance occurs. The RVP8 writes to the FIFO at full
speed as long as it is not full, and the internal processing is not affected by the exact speed at
which user I/O actually occurs. This continues as long as the average I/O rate on, perhaps 10ms
intervals, matches the average rate at which data are being produced.