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1b75d91002
Add arg to SATARep to specify drive types to show. Add checks in AHCIPortInit to verify port signatures, add helper method to get signatures from port.
42 lines
2.8 KiB
HTML
Executable file
42 lines
2.8 KiB
HTML
Executable file
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<pre style="font-family:monospace;font-size:12pt">
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<a name="l1"></a><span class=cF0>The </span><span class=cF2>Programmable Interval Timer</span><span class=cF0> has two purposes: Generate interrupts, and control the </span><span class=cF2>PC speaker</span><span class=cF0>.
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<a name="l2"></a>
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<a name="l3"></a>It has 3 channels:
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<a name="l4"></a></span><span class=cF4>
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<a name="l5"></a></span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KernelA.HH.html#l686"><span class=cF4>Channel 0</span></a><span class=cF0> can generate an interrupt, IRQ 0, at a defined frequency. We set it up in </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KMain.CC.html#l116"><span class=cF4>TimerInit</span></a><span class=cF0>(), and use it in </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KMisc.CC.html#l22"><span class=cF4>SysTimerRead</span></a><span class=cF0>().
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<a name="l6"></a>
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<a name="l7"></a>Channel 1 was used historically to refresh the DRAM, but now it is obsolete as the hardware does this itself. Channel 1 is
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<a name="l8"></a>useless and might not even be implemented anymore on modern machines.
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<a name="l9"></a></span><span class=cF4>
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<a name="l10"></a></span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KernelA.HH.html#l687"><span class=cF4>Channel 2</span></a><span class=cF0>'s output is connected to the PC speaker.
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<a name="l11"></a>
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<a name="l12"></a>The Command port is used to control each of these 3 channels. The relevant </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KernelA.HH.html#l690"><span class=cF4>flags</span></a><span class=cF0> are defined.
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<a name="l13"></a>
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<a name="l14"></a>See </span><a href="https://zeal-operating-system.github.io/ZealOS/Kernel/KMisc.CC.html#l129"><span class=cF4>Sound</span></a><span class=cF0>() for how the PC speaker frequency is changed.</span></pre></body>
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