1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<html> 3 4<head> 5<META http-equiv="Content-Type" content="text/html; charset=windows-1252"> 6<META name="GENERATOR" content="IBM WebSphere Studio Homepage Builder Version 7.0.0.0 for Windows"> 7<META http-equiv="Content-Style-Type" content="text/css"> 8<title>OS_GetVBlankCount</title> 9<LINK rel="stylesheet" href="../../css/nitro.css" type="text/css"> 10</head> 11 12<body> 13 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 <nitro/os.h></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 "interrupt."<br> 2004/08/10 Initial version.</P> 35<hr><p>CONFIDENTIAL</p></body> 36</html> 37
