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ATS9462 User Manual
Frequency (PRF) of 1 KHz or so, even though each capture
is only 2048 bytes (a paltry 2 MB/s throughput).
In other words, digitizers that specify raw data throughput of
100 MB/s can hardly handle 2MB/s effective throughput due
to operating system related delays in issuing re-arm
commands.
Real-Time Operating Systems
Some vendors claim that switching to a real-time operating
system (RTOS) can solve the problems involved in PRF data
capture.
Before switching to an expensive RTOS (such as VxWorks,
QNX or PharLap ETS), ask the vendor of the operating
system, the supplier of your PC system and manufacturer of
the digitizer board if they are all guaranteed to be 100%
compatible and interoperable with each other with
deterministic interrupt latencies and if you will get your money
back if the system does not work at your PRF rates with your
software.
Here is an excerpt from a FAQ section of one such supplier
of RTOS:
Question: How do system configuration and CPU selection
impact the interrupt latency?
Answer: Hardware platforms and the configuration of the
associated drivers that use the hardware do impact response
times. Some of the common issues include:
Video cards - some of the higher-end cards lock-out (or busy-
wait) the bus for extended periods of time to improve their
performance.
DMA devices - devices which burst DMA for lengthy period.
Power management which cycles off the CPU during IDLE CPU
periods.
Memory speeds, processor speeds, etc.
