/usr/share/doc/libcomedi-dev/html/g6679.html

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>    Glossary
  </TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="    Comedi
  "
HREF="index.html"><LINK
REL="PREVIOUS"
TITLE="comedi_get_softcal_converter"
HREF="r6633.html"></HEAD
><BODY
CLASS="GLOSSARY"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>Comedi: The <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>Control and Measurement Device Interface</I
></SPAN
>
handbook
  </TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="r6633.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
>&nbsp;</TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="GLOSSARY"
><H1
><A
NAME="COMEDILIB-GLOSSARY"
></A
>    Glossary
  </H1
><DL
><DT
><A
NAME="API"
></A
><B
>    Application Program Interface
    </B
></DT
> (API)<DD
><P
>The (documented) set of function calls supported by a particular
application, by which programmers can access the functionality
available in the application.
      </P
></DD
><DT
><A
NAME="BUFFER"
></A
><B
>buffer
    </B
></DT
><DD
><P
><ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> uses permanently allocated kernel memory for streaming input
and output to store data that has been measured by a device, but has
not been read by an application.  These buffers can be resized by the
Comedilib function <CODE
CLASS="FUNCTION"
>comedi_buffer_XXX()</CODE
> or the
<CODE
CLASS="FUNCTION"
>comedi_config</CODE
>
utility.
      </P
></DD
><DT
><A
NAME="BUFFEROVERFLOW"
></A
><B
>buffer overflow
    </B
></DT
><DD
><P
>This is an error message that indicates that the driver ran out of
space in a <ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> buffer to put samples.  It means that the application
is not copying data out of the buffer quickly enough.  Often, this
problem can be fixed by making the <ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> buffer larger.  See
<CODE
CLASS="FUNCTION"
>comedi_buffer_XXX</CODE
> for more information.
      </P
></DD
><DT
><A
NAME="DIFFERENTIALIO"
></A
><B
>    Differential IO
    </B
></DT
><DD
><P
>...
      </P
></DD
><DT
><A
NAME="DMA"
></A
><B
>    Direct Memory Access
    </B
></DT
> (DMA)<DD
><P
>DMA is a method of transferring data between
a device and the main memory of a computer.  DMA operates differently
on ISA and PCI cards.  ISA DMA is handled by a controller on the
motherboard and is limited to transfers to/from the lowest 16 MB of
physical RAM and can only handle a single segment of memory at a time.
These limitations make it almost useless.  PCI ("bus mastering") DMA
is handled by a controller on the device, and can typically address
4 GB of RAM and handle many segments of memory simultaneously.  DMA
is usually not the only means to data transfer, and may or may not
be the optimal transfer mechanism for a particular situation.
      </P
></DD
><DT
><A
NAME="FIFO"
></A
><B
>    First In, First Out
    </B
></DT
> (FIFO)<DD
><P
>Most devices have a limited amount of on-board space to store samples
before they are transferred to the Comedi buffer.  This allows the CPU or
DMA controller to do other things, and then efficiently process a
large number of samples simultaneously.  It also increases the
maximum interrupt latency that the system can handle without
interruptions in data.
      </P
></DD
><DT
><A
NAME="COMEDICOMMAND"
></A
><B
><ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> command
    </B
></DT
><DD
><P
><ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> commands are the mechanism that applications configure
subdevices for streaming input and output.
      </P
></DD
><DT
><A
NAME="COMMAND"
></A
><B
>command
    </B
></DT
><DD
><P
><EM
>See: </EM
><A
HREF="g6679.html#COMEDICOMMAND"
><ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> command
    </A
></P
></DD
><DT
><A
NAME="CONFIGOPTION"
></A
><B
>configuration option
    </B
></DT
><DD
><P
>      </P
></DD
><DT
><A
NAME="INSTRUCTION"
></A
><B
>instruction
    </B
></DT
><DD
><P
><ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> instructions are the mechanism used by applications to do
immediate input from channels, output to channels, and configuration
of subdevices and channels.
      </P
></DD
><DT
><A
NAME="INSTRUCTIONLIST"
></A
><B
>instruction list
    </B
></DT
><DD
><P
>Instruction lists allow the application to perform multiple <ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
>
instructions in the same system call.
      </P
></DD
><DT
><A
NAME="OPTION"
></A
><B
>option
    </B
></DT
><DD
><P
>      </P
><P
><EM
>See Also: </EM
><A
HREF="g6679.html#OPTIONLIST"
>option list
    </A
>.</P
></DD
><DT
><A
NAME="OPTIONLIST"
></A
><B
>option list
    </B
></DT
><DD
><P
>Option lists are used with <CODE
CLASS="FUNCTION"
>comedi_config</CODE
> to
perform driver configuration.
      </P
><P
><EM
>See Also: </EM
><A
HREF="g6679.html#CONFIGOPTION"
>configuration option
    </A
><EM
>, </EM
><A
HREF="g6679.html#OPTION"
>option
    </A
>.</P
></DD
><DT
><A
NAME="OVERRUN"
></A
><B
>overrun
    </B
></DT
><DD
><P
>This is an error message that indicates that there was device-level
problem, typically with trigger pulses occurring faster than the
board can handle.
      </P
></DD
><DT
><A
NAME="POLL"
></A
><B
>poll
    </B
></DT
><DD
><P
>The term poll (and polling) is used for several different related
concepts in <ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
>.  <ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
> implements the
<CODE
CLASS="FUNCTION"
>poll()</CODE
> system call for Comedi devices, which is
similar to <CODE
CLASS="FUNCTION"
>select()</CODE
>, and returns information
about file descriptors that can be read or written.  Comedilib also
has a function called <CODE
CLASS="FUNCTION"
>comedi_poll()</CODE
>, which causes
the driver to copy all available data from the device to the <ACRONYM
CLASS="ACRONYM"
>Comedi</ACRONYM
>
buffer.  In addition, some drivers may use a polling technique in
place of interrupts.
      </P
></DD
></DL
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="r6633.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>&nbsp;</TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>comedi_get_softcal_converter</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
>&nbsp;</TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>&nbsp;</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
libcomedi-dev 0.8.1-5ubuntu6 / usr / share / doc / libcomedi-dev / html / g6679.html
