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106 lines
4.0 KiB
C
106 lines
4.0 KiB
C
/*****************************************************************************/
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/* */
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/* memory.h */
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/* */
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/* Memory subsystem for the 6502 simulator */
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/* */
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/* */
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/* */
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/* (C) 2002-2012, Ullrich von Bassewitz */
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/* Roemerstrasse 52 */
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/* D-70794 Filderstadt */
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/* EMail: uz@cc65.org */
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/* */
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/* */
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/* This software is provided 'as-is', without any expressed or implied */
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/* warranty. In no event will the authors be held liable for any damages */
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/* arising from the use of this software. */
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/* */
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/* Permission is granted to anyone to use this software for any purpose, */
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/* including commercial applications, and to alter it and redistribute it */
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/* freely, subject to the following restrictions: */
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/* */
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/* 1. The origin of this software must not be misrepresented; you must not */
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/* claim that you wrote the original software. If you use this software */
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/* in a product, an acknowledgment in the product documentation would be */
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/* appreciated but is not required. */
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/* 2. Altered source versions must be plainly marked as such, and must not */
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/* be misrepresented as being the original software. */
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/* 3. This notice may not be removed or altered from any source */
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/* distribution. */
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/* */
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/*****************************************************************************/
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#include <string.h>
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#include "memory.h"
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/*****************************************************************************/
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/* Data */
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/*****************************************************************************/
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/* THE memory */
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static unsigned char Mem[0x10000];
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/*****************************************************************************/
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/* Code */
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/*****************************************************************************/
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void MemWriteByte (unsigned Addr, unsigned char Val)
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/* Write a byte to a memory location */
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{
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Mem[Addr] = Val;
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}
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unsigned char MemReadByte (unsigned Addr)
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/* Read a byte from a memory location */
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{
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return Mem[Addr];
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}
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unsigned MemReadWord (unsigned Addr)
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/* Read a word from a memory location */
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{
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unsigned W = MemReadByte (Addr++);
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return (W | (MemReadByte (Addr) << 8));
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}
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unsigned MemReadZPWord (unsigned char Addr)
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/* Read a word from the zero page. This function differs from ReadMemW in that
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** the read will always be in the zero page, even in case of an address
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** overflow.
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*/
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{
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unsigned W = MemReadByte (Addr++);
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return (W | (MemReadByte (Addr) << 8));
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}
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void MemInit (void)
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/* Initialize the memory subsystem */
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{
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/* Fill momory with illegal opcode */
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memset (Mem, 0xFF, sizeof (Mem));
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/* Set RESET vector to 0x0200 */
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Mem[0xFFFC] = 0x00;
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Mem[0xFFFD] = 0x02;
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}
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