There are many different (and often confusing) terms associated
with clock-based devices. This application note attempts
to clarify these terms, and hence serves as a comprehensive
reference on clock terminology. This application note can be
divided into two sections. The first section describes and distinguishes
between various clock sources available today.
The second section defines and distinguishes between various
parameters used to describe clocks. This section also provides methods of measuring some of these parameters.
Jitter is extremely important in systems using PLL-based
clock drivers. The effects of jitter range from not having any
effect on system operation to rendering the system completely
non-functional. This application note provides the reader
with a clear understanding of jitter in high-speed systems. It
introduces the reader to various kinds of jitter in high-speed
systems, their causes and their effects, and methods of reducing
jitter. This application note will concentrate on jitter in PLL-based frequency synthesizers.
Cypress Semiconductor makes a variety of PLL-based clock
generators. This application note provides a set of recommendations
to optimize usage of Cypress clock devices in a
system. The application note begins with recommended termination
techniques for clock generators. Subsequently, power
supply filtering and bypassing is discussed. Finally, the application
note provides some recommendations on board
layout.
The development of a data acquisition card based on USB bus is introduced in this article.It first describes the configuration and principle of this card in the part of hardware design,and then the application program and device driver in the part of software design.Data acquisition program in firmware is also discussed.Finally,this data acquisition card is tested and evaluated in a program developed by Lab Windows CVI,which shows that this car is stable and reliable
In a preemptive priority based RTOS, priority inversion
problem is among the major sources of deadline
violations. Priority inheritance protocol is one of the
approaches to reduce priority inversion. Unfortunately,
RTOS like uC/OS can’t support priority inheritance
protocol since it does not allow kernel to have multiple
tasks at the same priority. Although it has different ways
to avoid priority inversion such as priority ceiling
protocol, developers still have some difficulties in
programming real time applications with it. In this paper,
we redesign the uC/OS kernel to provide the ability to
support round robin scheduling and implement priority
inheritance semaphore on the modified kernel. As result,
we port new kernel with priority inheritance semaphore to
evaluation board, and evaluate the execution time of each
of the kernel service as well as verify the operations of
our implementation.
