NEC startWARE-GHS-Ravin-E, User Manual

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Chapter 4 Software Description
User’s Manual U17316EE1V0UM00
4.4.2 Benchmarks
Benchmarks is a program to test the performance of Ravin-E and the bus interface. It tests the speed of
vector and filled rectangle drawing as well as the data transfer between the host and Ravin-E. Bench-
marks measures certain key performance values under real-life rather than optimized idealistic condi-
tions. The selected screen resolution is 800 x 600 pixel at 60 Hz frame rate and two display layers are
enabled, one with 16 bit per pixel and the other one with 8 bit per pixel. In this configuration, the screen
refresh uses approximately 25% of the available bandwidth between Ravin-E and its SDRAMs. This is
an average bus load calculated for a whole frame and it includes the sync pulses, during which no data
transfer takes place at all. The average data rate during the display of a scan line is about twice as high
with short periods of essentially 100% bus load when a burst read is issued to fill the video output pipe-
line.
The times are measured with built-in timers on the V850E/ME2 and on the V
R
4131. The V
R
4131 timer
does not detect overflows and the arithmetic has been chosen to make a compromise between preci-
sion and integer overflow in intermediate results. Therefore when changing the code, especially the
number of loops, note that overflows on the V
R
4131 are not detected and they may return invalid
results. Also the timers are configured for the documented operating speeds. Make sure to adapt the
initialization, if the clock speed deviates from the reference clock speed. Note that the results of the tim-
ing measurements vary in a certain range due to the statistical nature of the accesses on the Ravin-E
frame buffer.
The effect of write combining can be tested by defining NO_WC at compile time. Write combining is
enabled by default. It enables Ravin-E to combine write transfers to subsequent memory addresses
and to make burst accesses instead of single writes. That has a very noticeable effect if data is usually
written to subsequent addresses. Writes to random addresses are slowed down, however, because
every individual write access is delayed, as it might have to be combined with the next write.
4.4.3 Datalogger
Datalogger is an application, which displays a simple four channel datalogger grid on the foreground
layer. This is a pre-defined image that is stored in a PNG-file and extracted once at initialization time
into the frame buffer. Four traces are displayed on the background layer, which move from the right side
to the left, so that the older values appear on the left and the newer values on the right side. The dis-
played values are generated from pseudo random numbers which are low pass filtered to make them
look like real analogue input data.
Display of the trace lines makes use of Ravin-E's feature to move the viewport freely over the virtual dis-
play area. When the display line wraps over, Ravin-E does not actually display the image data from the
subsequent line, but the data from the beginning of the current line. This feature permits the impression
of a moving image, without actually copying data within the frame buffer. Only the start address of the
viewport is constantly updated. In the case of the datalogger demo program, the right most column is
updated in addition to the viewport address, as always new data shall be displayed. The display data is
erased on the left side of the screen, before it enters the outside of the grid.
The datalogger demo program requires very little CPU performance. Almost all CPU time is spent in the
“os_sleep(20)” delay at the end of function main.
4.4.4 HW-Test
HW-Test is a program, which is used by NEC in the startWARE-GHS-Ravin-E production test. It per-
forms an initial test of the Ravin-E frame buffer memory, displays some vectors with colour shading on
the screen and captures a video via the cinch connectors.