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<title>StreamDevice: ao Records</title>
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<h1>ao Records</h1>
<h2>Normal Operation</h2>
<p>
Depending on the format type, different record fields are used
for output and input. The variable <code><i>x</i></code> stands for the
written or read value.
</p>
<dl>
<dt>DOUBLE format (e.g. <code>%f</code>):</dt>
<dd>
<u>Output:</u> <code><i>x</i>=(OVAL-AOFF)/ASLO</code><br>
<u>Input:</u> <code>VAL=<i>x</i>*ASLO+AOFF</code><br>
In both cases, if <code>ASLO==0.0</code>, it is treated as <code>1.0</code>.
Default values are <code>ASLO=1.0</code>, <code>AOFF=0.0</code>.<br>
Note that <code>OVAL</code> is not necessarily equal to <code>VAL</code>
if <code>OROC!=0.0</code>.
</dd>
<dt>LONG format (e.g. <code>%i</code>):</dt>
<dd>
<u>Output:</u> <code><i>x</i>=RVAL</code><br>
<u>Input:</u> <code>RBV=<i>x</i></code><br>
Note that the record calculates
<code>RVAL=(((OVAL-EOFF)/ESLO)-AOFF)/ASLO</code> if
<code>LINR=="LINEAR"</code>. <code>ESLO</code> and <code>EOFF</code>
might be set in the record definition. <em>StreamDevice</em> does not set it.
For example, <code>EOFF=-10</code> and <code>ESLO=0.000305180437934</code>
(=20.0/0xFFFF) maps -10.0 to 0x0000, 0.0 to 0x7FFF and 10.0 to 0xFFFF.
Using unsigned formats with values &ge; 0x800000 gives different results
on 64 bit machines.
<p>
If <code>LINR=="NO CONVERSION"</code> (the default), <code>OVAL</code>
is directly converted to <code>long</code> without going through
<code>RVAL</code>. This allows for more bits on 64 bit machines.
To get the old behavior, use <code>LINR=="LINEAR"</code>.
</p>
</dd>
<dt>ENUM format (e.g. <code>%{</code>):</dt>
<dd>
Not allowed.
</dd>
<dt>STRING format (e.g. <code>%s</code>):</dt>
<dd>
Not allowed.
</dd>
</dl>
<h2>Initialization</h2>
<p>
During <a href="processing.html#init">initialization</a>, the <code>@init</code> handler is executed, if
present. In contrast to normal operation, output in DOUBLE format uses
<code>VAL</code> instead of <code>OVAL</code>. Note that the record
initializes <code>VAL</code> from <code>DOL</code> if that is a constant.
LONG input is put to <code>RVAL</code> as well as to <code>RBV</code> and
converted by the record.
</p>
<hr>
<p>
<a href="aai.html">aai</a>
<a href="aao.html">aao</a>
<a href="ai.html">ai</a>
<a href="bi.html">bi</a>
<a href="bo.html">bo</a>
<a href="mbbi.html">mbbi</a>
<a href="mbbo.html">mbbo</a>
<a href="mbbiDirect.html">mbbiDirect</a>
<a href="mbboDirect.html">mbboDirect</a>
<a href="longin.html">longin</a>
<a href="longout.html">longout</a>
<a href="stringin.html">stringin</a>
<a href="stringout.html">stringout</a>
<a href="waveform.html">waveform</a>
<a href="calcout.html">calcout</a>
<a href="scalcout.html">scalcout</a>
</p>
<p><small>Dirk Zimoch, 2015</small></p>
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