Instrumentation APIs
3-22
Although statistics are accumulated in 32-bit variables on the target, they are
accumulated in 64-bit variables on the host. When the host polls the target for
real-time statistics, it resets the variables on the target. This minimizes space
requirements on the target while allowing you to keep statistics for long test
runs. The Statistics Data tool can optionally filter the data arithmetically before
displaying it as shown in Figure 3-2.
Figure 3-2. Target/Host Variable Accumulation
By clearing the values on the target, the host allows the values displayed to
be much larger without risking lost data due to values on the target wrapping
around to 0. If polling of STS data is disabled or very infrequent, there is a
possibility that the STS data wraps around, resulting in incorrect information.
While the host clears the values on the target automatically, you can clear the
64-bit objects stored on the host by right-clicking on the STS Data window
and choosing Clear from the shortcut menu.
The host read and clear operations are performed with interrupts disabled to
allow any thread to update any STS object reliably. For example, an HWI
function can call STS_add on an STS object and no data is missing from any
STS fields.
This instrumentation process provides minimal intrusion into the target
program. A call to STS_add requires approximately 20 instructions on the
C5000 platform and 18 instructions on the C6000 platform. Similarly, an STS
object uses only eight or four words of data memory on the C5000 or C6000
platforms, respectively. Data filtering, formatting, and computation of the
average is done on the host.
You can control the polling rate for statistics information with the RTA Control
Panel Property Page. If you set the polling rate to 0, the host does not poll the
target for information about the STS objects unless you right-click on the
Statistics Data tool and choose Refresh Window from the pop-up menu.
Target
Host
read
&
clear
Accumulate Filter = (A*x + B) / C Display
Count
(A x total + B) / C
(A x max + B) / C
Count
Total
Maximum
Count
Total
0 Max
32
Previous
Count
Total
Max
Average
(A x total + B) /
(C x count)
64
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