konami.c

来自「这个是延伸mame的在wince平台下的游戏模拟器的代码」· C语言 代码 · 共 40 行

/***************************************************************************

  The Konami_1 CPU is a 6809 with opcodes scrambled. Here is how to
  descramble them.

***************************************************************************/

#include "driver.h"



unsigned char KonamiDecode( unsigned char opcode, unsigned short address )
{
/*
>
> CPU_D7 = (EPROM_D7 & ~ADDRESS_1) | (~EPROM_D7 & ADDRESS_1)  >
> CPU_D6 = EPROM_D6
>
> CPU_D5 = (EPROM_D5 & ADDRESS_1) | (~EPROM_D5 & ~ADDRESS_1) >
> CPU_D4 = EPROM_D4
>
> CPU_D3 = (EPROM_D3 & ~ADDRESS_3) | (~EPROM_D3 & ADDRESS_3) >
> CPU_D2 = EPROM_D2
>
> CPU_D1 = (EPROM_D1 & ADDRESS_3) | (~EPROM_D1 & ~ADDRESS_3) >
> CPU_D0 = EPROM_D0
>
*/
	unsigned char xormask;


	xormask = 0;
	if (address & 0x02) xormask |= 0x80;
	else xormask |= 0x20;
	if (address & 0x08) xormask |= 0x08;
	else xormask |= 0x02;

	return opcode ^ xormask;
}