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mathbox.c
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C/C++ Source or Header
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2000-04-23
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7KB
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278 lines
/*
* mathbox.c: math box simulation (Battlezone/Red Baron/Tempest)
*
* Copyright 1991, 1992, 1993, 1996 Eric Smith
*
* $Header: /usr2/eric/vg/atari/vecsim/RCS/mathbox.c,v 1.1 1996/08/29 07:23:59 eric Exp eric $
*/
#include "driver.h"
#include "mathbox.h"
/* math box scratch registers */
s16 mb_reg [16];
/* math box result */
s16 mb_result = 0;
#define REG0 mb_reg [0x00]
#define REG1 mb_reg [0x01]
#define REG2 mb_reg [0x02]
#define REG3 mb_reg [0x03]
#define REG4 mb_reg [0x04]
#define REG5 mb_reg [0x05]
#define REG6 mb_reg [0x06]
#define REG7 mb_reg [0x07]
#define REG8 mb_reg [0x08]
#define REG9 mb_reg [0x09]
#define REGa mb_reg [0x0a]
#define REGb mb_reg [0x0b]
#define REGc mb_reg [0x0c]
#define REGd mb_reg [0x0d]
#define REGe mb_reg [0x0e]
#define REGf mb_reg [0x0f]
/*define MB_TEST*/
WRITE_HANDLER( mb_go_w )
{
s32 mb_temp; /* temp 32-bit multiply results */
s16 mb_q; /* temp used in division */
int msb;
#ifdef MB_TEST
logerror("math box command %02x data %02x ", offset, data);
#endif
switch (offset)
{
case 0x00: mb_result = REG0 = (REG0 & 0xff00) | data; break;
case 0x01: mb_result = REG0 = (REG0 & 0x00ff) | (data << 8); break;
case 0x02: mb_result = REG1 = (REG1 & 0xff00) | data; break;
case 0x03: mb_result = REG1 = (REG1 & 0x00ff) | (data << 8); break;
case 0x04: mb_result = REG2 = (REG2 & 0xff00) | data; break;
case 0x05: mb_result = REG2 = (REG2 & 0x00ff) | (data << 8); break;
case 0x06: mb_result = REG3 = (REG3 & 0xff00) | data; break;
case 0x07: mb_result = REG3 = (REG3 & 0x00ff) | (data << 8); break;
case 0x08: mb_result = REG4 = (REG4 & 0xff00) | data; break;
case 0x09: mb_result = REG4 = (REG4 & 0x00ff) | (data << 8); break;
case 0x0a: mb_result = REG5 = (REG5 & 0xff00) | data; break;
/* note: no function loads low part of REG5 without performing a computation */
case 0x0c: mb_result = REG6 = data; break;
/* note: no function loads high part of REG6 */
case 0x15: mb_result = REG7 = (REG7 & 0xff00) | data; break;
case 0x16: mb_result = REG7 = (REG7 & 0x00ff) | (data << 8); break;
case 0x1a: mb_result = REG8 = (REG8 & 0xff00) | data; break;
case 0x1b: mb_result = REG8 = (REG8 & 0x00ff) | (data << 8); break;
case 0x0d: mb_result = REGa = (REGa & 0xff00) | data; break;
case 0x0e: mb_result = REGa = (REGa & 0x00ff) | (data << 8); break;
case 0x0f: mb_result = REGb = (REGb & 0xff00) | data; break;
case 0x10: mb_result = REGb = (REGb & 0x00ff) | (data << 8); break;
case 0x17: mb_result = REG7; break;
case 0x19: mb_result = REG8; break;
case 0x18: mb_result = REG9; break;
case 0x0b:
REG5 = (REG5 & 0x00ff) | (data << 8);
REGf = (s16)0xffff;
REG4 -= REG2;
REG5 -= REG3;
step_048:
mb_temp = ((s32) REG0) * ((s32) REG4);
REGc = mb_temp >> 16;
REGe = mb_temp & 0xffff;
mb_temp = ((s32) -REG1) * ((s32) REG5);
REG7 = mb_temp >> 16;
mb_q = mb_temp & 0xffff;
REG7 += REGc;
/* rounding */
REGe = (REGe >> 1) & 0x7fff;
REGc = (mb_q >> 1) & 0x7fff;
mb_q = REGc + REGe;
if (mb_q < 0)
REG7++;
mb_result = REG7;
if (REGf < 0)
break;
REG7 += REG2;
/* fall into command 12 */
case 0x12:
mb_temp = ((s32) REG1) * ((s32) REG4);
REGc = mb_temp >> 16;
REG9 = mb_temp & 0xffff;
mb_temp = ((s32) REG0) * ((s32) REG5);
REG8 = mb_temp >> 16;
mb_q = mb_temp & 0xffff;
REG8 += REGc;
/* rounding */
REG9 = (REG9 >> 1) & 0x7fff;
REGc = (mb_q >> 1) & 0x7fff;
REG9 += REGc;
if (REG9 < 0)
REG8++;
REG9 <<= 1; /* why? only to get the desired load address? */
mb_result = REG8;
if (REGf < 0)
break;
REG8 += REG3;
REG9 &= 0xff00;
/* fall into command 13 */
case 0x13:
#ifdef MB_TEST
logerror("\nR7: %04x R8: %04x R9: %04x\n", REG7, REG8, REG9);
#endif
REGc = REG9;
mb_q = REG8;
goto step_0bf;
case 0x14:
REGc = REGa;
mb_q = REGb;
step_0bf:
REGe = REG7 ^ mb_q; /* save sign of result */
REGd = mb_q;
if (mb_q >= 0)
mb_q = REGc;
else
{
REGd = - mb_q - 1;
mb_q = - REGc - 1;
if ((mb_q < 0) && ((mb_q + 1) < 0))
REGd++;
mb_q++;
}
/* step 0c9: */
/* REGc = abs (REG7) */
if (REG7 >= 0)
REGc = REG7;
else
REGc = -REG7;
REGf = REG6; /* step counter */
do
{
REGd -= REGc;
msb = ((mb_q & 0x8000) != 0);
mb_q <<= 1;
if (REGd >= 0)
mb_q++;
else
REGd += REGc;
REGd <<= 1;
REGd += msb;
}
while (--REGf >= 0);
if (REGe >= 0)
mb_result = mb_q;
else
mb_result = - mb_q;
break;
case 0x11:
REG5 = (REG5 & 0x00ff) | (data << 8);
REGf = 0x0000; /* do everything in one step */
goto step_048;
break;
case 0x1c:
/* window test? */
REG5 = (REG5 & 0x00ff) | (data << 8);
do
{
REGe = (REG4 + REG7) >> 1;
REGf = (REG5 + REG8) >> 1;
if ((REGb < REGe) && (REGf < REGe) && ((REGe + REGf) >= 0))
{ REG7 = REGe; REG8 = REGf; }
else
{ REG4 = REGe; REG5 = REGf; }
}
while (--REG6 >= 0);
mb_result = REG8;
break;
case 0x1d:
REG3 = (REG3 & 0x00ff) | (data << 8);
REG2 -= REG0;
if (REG2 < 0)
REG2 = -REG2;
REG3 -= REG1;
if (REG3 < 0)
REG3 = -REG3;
/* fall into command 1e */
case 0x1e:
/* result = max (REG2, REG3) + 3/8 * min (REG2, REG3) */
if (REG3 >= REG2)
{ REGc = REG2; REGd = REG3; }
else
{ REGd = REG2; REGc = REG3; }
REGc >>= 2;
REGd += REGc;
REGc >>= 1;
mb_result = REGd = (REGc + REGd);
break;
case 0x1f:
logerror("math box function 0x1f\n");
/* $$$ do some computation here (selftest? signature analysis? */
break;
}
#ifdef MB_TEST
logerror(" result %04x\n", mb_result & 0xffff);
#endif
}
READ_HANDLER( mb_status_r )
{
return 0x00; /* always done! */
}
READ_HANDLER( mb_lo_r )
{
return mb_result & 0xff;
}
READ_HANDLER( mb_hi_r )
{
return (mb_result >> 8) & 0xff;
}