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76 lines
1.8 KiB
C
76 lines
1.8 KiB
C
/*
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* PROJECT: NEC PC-98 series HAL
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* LICENSE: GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
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* PURPOSE: PIT rollover tables
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* COPYRIGHT: Copyright 2020 Dmitry Borisov (di.sean@protonmail.com)
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*/
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/* INCLUDES ******************************************************************/
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#include <hal.h>
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/* GLOBALS *******************************************************************/
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#define LPT_STATUS 0x42
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#define SYSTEM_CLOCK_8_MHZ 0x20
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ULONG PIT_FREQUENCY;
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HALP_ROLLOVER HalpRolloverTable[15];
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/* Accuracy is 97.5% */
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static const HALP_ROLLOVER RolloverTable1[15] =
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{
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{1996, 9996}, /* 1 ms */
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{3993, 19997},
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{5990, 29998},
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{7987, 39999},
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{9984, 50000},
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{11980, 59996},
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{13977, 69997},
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{15974, 79998},
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{17971, 89999},
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{19968, 100000},
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{21964, 109996},
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{23961, 119997},
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{25958, 129998},
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{27955, 139999},
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{29951, 149995} /* 15 ms */
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};
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static const HALP_ROLLOVER RolloverTable2[15] =
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{
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{2463, 10022}, /* 1 ms */
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{4912, 19987},
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{7376, 30013},
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{9825, 39978},
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{12288, 50000},
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{14751, 60022},
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{17200, 69987},
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{19664, 80013},
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{22113, 89978},
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{24576, 100000},
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{27039, 110022},
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{29488, 119987},
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{31952, 130013},
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{34401, 139978},
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{36864, 150000} /* 15 ms */
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};
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/* PRIVATE FUNCTIONS *********************************************************/
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VOID
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NTAPI
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HalpInitializeClockPc98(VOID)
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{
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/* Obtain system clock value from the parallel port */
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if (__inbyte(LPT_STATUS) & SYSTEM_CLOCK_8_MHZ)
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{
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PIT_FREQUENCY = TIMER_FREQUENCY_1;
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RtlCopyMemory(HalpRolloverTable, RolloverTable1, sizeof(HALP_ROLLOVER) * 15);
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}
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else
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{
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PIT_FREQUENCY = TIMER_FREQUENCY_2;
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RtlCopyMemory(HalpRolloverTable, RolloverTable2, sizeof(HALP_ROLLOVER) * 15);
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}
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}
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