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14<h1 align="left">OS_GetVBlankCount <IMG src="../../image/NTR.gif" align="middle"><IMG src="../../image/TWL.gif" align="middle"></h1>
15<h2>Syntax</h2>
16
17<dl>
18  <dd>
19<CODE>#include &lt;nitro/os.h&gt;</CODE><BR>
20  <BR>
21  <CODE>u32 OS_GetVBlankCount( void );</CODE></dd>
22</dl><h2>Arguments</h2>
23<P>None.</P>
24<h2>Return Values</h2>
25<p>Returns the V-blank counter value.</p>
26<H2>Description</H2>
27<p>Obtains the value of the V-Blank counter.</p>
28<p>The V-blank counter is incremented with V-blank timing. It is cleared to 0 when the IRQ table is initialized. Once initialized, the counter is incremented whenever a V-blank interrupt occurs. The counter is u32 type; in calculations that use 60 frames per second, it takes about two years for the counter to roll over.</p>
29<p>The counter is incremented when the ARM7 bus tries to call the V-blank interrupt handler, and writes to the shared main memory area. Therefore, when V-blank is not included in the IRQ interrupt trigger on the ARM7, or when IME is disabled, the counter does not change unless the part that calls the V-blank interrupt handler is reached. If a V-blank interrupt is permitted on ARM7, the counter is incremented even if the V-blank interrupt handler is not set.</p>
30<h2>See Also</h2>
31<p>None.</p>
32<H2>Revision History</H2>
33<P>
342005/03/08 Standardized the Japanese term for &quot;interrupt.&quot;<br> 2004/08/10 Initial version.</P>
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