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+/*
+ 3dsspec - Nintendo 3DS Spectrum emulator
+
+ Copyright (C) 2021 Ian Cowburn <ianc@noddybox.co.uk>
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, see <http://www.gnu.org/licenses/>
+
+ -------------------------------------------------------------------------
+
+ Provides the emulation for the Spectrum
+
+*/
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <ctype.h>
+#include <3ds.h>
+
+#include "spec.h"
+#include "gui.h"
+#include "framebuffer.h"
+
+#include "stream.h"
+
+#include "config.h"
+
+#include "spec48_bin.h"
+
+#ifndef TRUE
+#define TRUE 1
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+/* ---------------------------------------- STATICS
+*/
+#define ROMLEN 0x4000
+#define ROM_SAVE 0x2fc
+#define ROM_LOAD 0x347
+
+#define ED_SAVE 0xf0
+#define ED_LOAD 0xf1
+
+#define SLOW_TSTATES 16000
+#define FAST_TSTATES 64000
+
+#define E_LINE 16404
+#define LASTK1 16421
+#define LASTK2 16422
+#define MARGIN 16424
+#define FRAMES 16436
+#define CDFLAG 16443
+
+#define NMI_PERIOD 208
+
+/* The SPEC screen and memory
+*/
+static int fast_mode=FALSE;
+static int nmigen=FALSE;
+static int hsync=FALSE;
+static int drawing_screen=FALSE;
+static int ula_line_counter;
+
+static u16 black;
+static u16 white;
+
+#define SCR_W 256
+#define SCR_H 192
+#define TXT_W 32
+#define TXT_H 24
+
+static Z80Byte mem[0x10000];
+
+static u16 screen[SCR_W*SCR_H];
+static int ula_ptr;
+
+static Z80Word RAMBOT=0;
+static Z80Word RAMTOP=0;
+
+#define DFILE 0x400c
+
+#define WORD(a) (mem[a] | (Z80Word)mem[a+1]<<8)
+
+/* Tape
+*/
+static int enable_filesystem;
+static int allow_save;
+static const Z80Byte *tape_image;
+static int tape_len;
+
+static char last_dir[FILENAME_MAX] = "/";
+
+/* The keyboard
+*/
+static Z80Byte matrix[8];
+
+static struct
+{
+ int row;
+ int bit;
+} key_matrix[]=
+ {
+ {3,0x01}, {3,0x02}, {3,0x04}, {3,0x08}, {3,0x10}, /* 1 - 5 */
+ {4,0x10}, {4,0x08}, {4,0x04}, {4,0x02}, {4,0x01}, /* 6 - 0 */
+ {2,0x01}, {2,0x02}, {2,0x04}, {2,0x08}, {2,0x10}, /* Q - T */
+ {5,0x10}, {5,0x08}, {5,0x04}, {5,0x02}, {5,0x01}, /* Y - P */
+ {1,0x01}, {1,0x02}, {1,0x04}, {1,0x08}, {1,0x10}, /* A - G */
+ {6,0x10}, {6,0x08}, {6,0x04}, {6,0x02}, {6,0x01}, /* H - NL */
+ {0,0x01}, {0,0x02}, {0,0x04}, {0,0x08}, {0,0x10}, /* CAPS - V */
+ {7,0x10}, {7,0x08}, {7,0x04}, {7,0x02}, {7,0x01} /* B - SPACE */
+ };
+
+
+/* ---------------------------------------- PRIVATE FUNCTIONS
+*/
+#define PEEKW(addr) (mem[addr] | (Z80Word)mem[addr+1]<<8)
+
+#define POKEW(addr,val) do \
+ { \
+ Z80Word wa=addr; \
+ Z80Word wv=val; \
+ mem[wa]=wv; \
+ mem[wa+1]=wv>>8; \
+ } while(0)
+
+static void RomPatch(void)
+{
+ static const Z80Byte save[]=
+ {
+ 0xed, ED_SAVE, /* (SAVE) */
+ 0xc3, 0x07, 0x02, /* JP $0207 */
+ 0xff /* End of patch */
+ };
+
+ static const Z80Byte load[]=
+ {
+ 0xed, ED_LOAD, /* (LOAD) */
+ 0xc3, 0x07, 0x02, /* JP $0207 */
+ 0xff /* End of patch */
+ };
+
+ int f;
+
+ for(f=0;save[f]!=0xff;f++)
+ {
+ mem[ROM_SAVE+f]=save[f];
+ }
+
+ for(f=0;load[f]!=0xff;f++)
+ {
+ mem[ROM_LOAD+f]=load[f];
+ }
+}
+
+/* Open a tape file the passed address
+*/
+static FILE *OpenTapeFile(Z80Word addr, int *cancelled, const char *mode)
+{
+ static const char zx_chars[] = "\"#$:?()><=+-*/;,."
+ "0123456789"
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+ FILE *fp;
+ char full_fn[FILENAME_MAX] = DEFAULT_SNAPDIR;
+ char fn[FILENAME_MAX];
+ int f;
+ int done;
+
+ fp = NULL;
+ f = 0;
+ done = FALSE;
+ *cancelled = FALSE;
+
+ while(f<(FILENAME_MAX-3) && !done)
+ {
+ int ch;
+
+ ch = mem[addr++];
+
+ if (ch&0x80)
+ {
+ done = TRUE;
+ ch &= 0x7f;
+ }
+
+ if (ch>=11 && ch<=63)
+ {
+ fn[f++] = zx_chars[ch-11];
+ }
+ }
+
+ if (fn[0] == '*')
+ {
+ if (GUI_FileSelect(last_dir,fn,".P"))
+ {
+ fp = fopen(fn, mode);
+ }
+ else
+ {
+ *cancelled = TRUE;
+ }
+
+ SK_DisplayKeyboard();
+ }
+ else
+ {
+ fn[f++] = '.';
+ fn[f++] = 'P';
+ fn[f] = 0;
+
+ strcat(full_fn,fn);
+
+ if (!(fp = fopen(full_fn, mode)))
+ {
+ fp = fopen(fn, mode);
+ }
+ }
+
+ return fp;
+}
+
+
+static void LoadInternalTape(Z80 *z80)
+{
+ memcpy(mem+0x4009,tape_image,tape_len);
+}
+
+
+static void LoadExternalTape(FILE *tape, Z80 *z80)
+{
+ int c;
+ Z80Byte *a;
+
+ a=mem+0x4009;
+
+ while((c=getc(tape))!=EOF)
+ {
+ *a++=c;
+ }
+}
+
+
+static void SaveExternalTape(FILE *tape, Z80 *z80)
+{
+ int f;
+ int end;
+
+ f = 0x4009;
+ end = WORD(E_LINE);
+
+ while(f <= end)
+ {
+ fputc(mem[f++], tape);
+ }
+}
+
+
+static int CheckTimers(Z80 *z80, Z80Val val)
+{
+ static Z80Word last_PC;
+ static Z80Byte last_R;
+ int ret = TRUE;
+
+ /* See if we're started or stopping executing the display file
+ */
+ if (z80->PC > 0x7fff)
+ {
+ if (last_PC < 0x8000)
+ {
+ drawing_screen = TRUE;
+ ula_ptr = 0;
+ }
+ }
+
+ if (z80->PC < 0x8000)
+ {
+ if (last_PC > 0x7fff && ula_ptr == SCR_W * SCR_H)
+ {
+ drawing_screen = FALSE;
+ ula_ptr = 0;
+ Z80ResetCycles(z80, val - SLOW_TSTATES);
+ ret = FALSE;
+ }
+ }
+
+ last_PC = z80->PC;
+
+ /* Check HSYNC generation
+ */
+ if (hsync && !nmigen)
+ {
+ if (last_R & 0x40 && !(z80->R & 0x40))
+ {
+ Z80Interrupt(z80, 0xff);
+ ula_line_counter = (ula_line_counter + 1) % 8;
+ }
+ }
+
+ last_R = z80->R;
+
+ /* Check NMI generator
+ */
+ if (nmigen && val > NMI_PERIOD)
+ {
+ Z80NMI(z80);
+ Z80ResetCycles(z80, val - NMI_PERIOD);
+ }
+
+ /* We should only be able to execute FAST_TSTATES if we're not drawing the
+ screen.
+ */
+ if (val >= FAST_TSTATES)
+ {
+ Z80ResetCycles(z80,val-FAST_TSTATES);
+
+ if (mem[CDFLAG] & 0x80)
+ {
+ fast_mode = FALSE;
+ }
+ else
+ {
+ fast_mode = TRUE;
+ }
+
+ ret = FALSE;
+ }
+
+ return ret;
+}
+
+
+static int EDCallback(Z80 *z80, Z80Val data)
+{
+ switch((Z80Byte)data)
+ {
+ case ED_SAVE:
+ if (allow_save && z80->DE.w<0x8000)
+ {
+ FILE *fp;
+ int cancel;
+
+ if ((fp=OpenTapeFile(z80->HL.w, &cancel, "wb")))
+ {
+ SaveExternalTape(fp,z80);
+ fclose(fp);
+ }
+ }
+ break;
+
+ case ED_LOAD:
+ /* Try and load the external file if a name given. Otherwise, we
+ try the internal one. Some of this is slightly dodgy -- it was
+ never intended for the emulator to be doing any GUI related
+ nonsense (like the alerts) but simply emulating.
+ */
+ if (enable_filesystem && z80->DE.w<0x8000)
+ {
+ FILE *fp;
+ int cancel;
+
+ if ((fp=OpenTapeFile(z80->DE.w, &cancel, "rb")))
+ {
+ LoadExternalTape(fp,z80);
+ fclose(fp);
+ }
+ else
+ {
+ if (!cancel)
+ {
+ GUI_Alert(FALSE,"Couldn't open tape");
+ SK_DisplayKeyboard();
+ }
+ }
+ }
+ else
+ {
+ if (tape_image)
+ {
+ LoadInternalTape(z80);
+ }
+ else
+ {
+ GUI_Alert(FALSE,"No tape image selected");
+ SK_DisplayKeyboard();
+ }
+ }
+
+ mem[CDFLAG]=0xc0;
+ break;
+
+ default:
+ break;
+ }
+
+ return TRUE;
+}
+
+
+/* ---------------------------------------- EXPORTED INTERFACES
+*/
+void SPECInit(Z80 *z80)
+{
+ Z80Word f;
+
+ black = FB_GetColour(COL_BLACK);
+ white = FB_GetColour(COL_WHITE);
+
+ /* Load the ROM
+ */
+ memcpy(mem,spec48_bin,ROMLEN);
+
+ /* Patch the ROM
+ */
+ RomPatch();
+ Z80LodgeCallback(z80,eZ80_EDHook,EDCallback);
+ Z80LodgeCallback(z80,eZ80_Instruction,CheckTimers);
+
+ /* Mirror the ROM
+ */
+ memcpy(mem+ROMLEN,mem,ROMLEN);
+
+ /* Memory size (16K)
+ */
+ RAMBOT=0x4000;
+ RAMTOP=RAMBOT+0x4000;
+
+ for(f = RAMBOT; f <= RAMTOP; f++)
+ {
+ mem[f] = 0;
+ }
+
+ for(f = 0; f < 8; f++)
+ {
+ matrix[f] = 0x1f;
+ }
+}
+
+
+void SPECRenderDisplay(Framebuffer *fb, Z80 *z80)
+{
+ if (fast_mode)
+ {
+ u16 x;
+ u16 y;
+
+ for(x = 0; x < fb->width; x++)
+ {
+ for(y = 0; y < fb->height; y++)
+ {
+ FB_ADDR(fb, x, y) = ((x+y) % 2) ? black : white;
+ }
+ }
+ }
+ else
+ {
+ int x;
+ int y;
+
+ FB_Clear(fb, COL_WHITE);
+
+ for(y = 0; y < SCR_H; y++)
+ {
+ for(x = 0; x < SCR_W; x++)
+ {
+ FB_ADDR(fb, 72 + x, fb->height - 24 - y) =
+ screen[x + y * SCR_W];
+ }
+ }
+ }
+}
+
+
+void SPECHandleKey(SoftKey key, int is_pressed)
+{
+ if (key<SK_CONFIG)
+ {
+ if (is_pressed)
+ {
+ matrix[key_matrix[key].row]&=~key_matrix[key].bit;
+ }
+ else
+ {
+ matrix[key_matrix[key].row]|=key_matrix[key].bit;
+ }
+ }
+ else
+ {
+ /* TODO: Joysticks? Were there any common ones for the 81? */
+ }
+}
+
+
+Z80Byte SPECReadMem(Z80 *z80, Z80Word addr)
+{
+ if (addr & 0x8000)
+ {
+ Z80Byte b;
+
+ b = mem[addr & 0x7fff];
+
+ /* If bit 6 of the byte is set it is sent to the CPU, otherwise it is
+ used to generate the video signal and zero sent to the CPU
+ */
+ if (b & 0x40)
+ {
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ screen[ula_ptr++] = white;
+ }
+ else
+ {
+ Z80Word base;
+ int inv;
+ int f;
+
+ inv=b & 0x80;
+ b &= 0x3f;
+
+ base = ((Z80Word)z80->I<<8)|(b<<3)|ula_line_counter;
+
+ b = mem[base];
+
+ for(f = 0; f < 8; f++)
+ {
+ if (b & 0x80)
+ {
+ screen[ula_ptr++] = rand(); // inv ? white : black;
+ }
+ else
+ {
+ screen[ula_ptr++] = rand(); // inv ? black : white;
+ }
+
+ b = b << 1;
+ }
+
+ b = 0;
+ }
+
+ return b;
+ }
+ else
+ {
+ return mem[addr];
+ }
+}
+
+
+void SPECWriteMem(Z80 *z80, Z80Word addr, Z80Byte val)
+{
+ if (addr>=RAMBOT && addr<=RAMTOP)
+ {
+ mem[addr]=val;
+ }
+}
+
+
+Z80Byte SPECReadPort(Z80 *z80, Z80Word port)
+{
+ Z80Byte b=0;
+
+ switch(port&0xff)
+ {
+ case 0xfe: /* ULA */
+ /* Key matrix
+ */
+ switch(port&0xff00)
+ {
+ case 0xfe00:
+ b=matrix[0];
+ break;
+ case 0xfd00:
+ b=matrix[1];
+ break;
+ case 0xfb00:
+ b=matrix[2];
+ break;
+ case 0xf700:
+ b=matrix[3];
+ break;
+ case 0xef00:
+ b=matrix[4];
+ break;
+ case 0xdf00:
+ b=matrix[5];
+ break;
+ case 0xbf00:
+ b=matrix[6];
+ break;
+ case 0x7f00:
+ b=matrix[7];
+ break;
+ }
+
+ /* Some code expects some of the top bits set... Of course, whether
+ or not this may be worse as other code doesn't expect the bits,
+ we shall find out!
+ */
+ b |= 0x60;
+
+ /* Reset ULA line counter
+ */
+ ula_line_counter = 0;
+
+ break;
+
+ default:
+ b = 0xff; /* Idle bus */
+ break;
+ }
+
+ return b;
+}
+
+
+void SPECWritePort(Z80 *z80, Z80Word port, Z80Byte val)
+{
+ switch(port&0xff)
+ {
+ case 0xfd: /* NMI generator OFF */
+ nmigen = FALSE;
+ break;
+
+ case 0xfe: /* NMI generator ON */
+ nmigen = TRUE;
+ Z80ResetCycles(z80, 0);
+ break;
+
+ case 0xff: /* HSYNC generator ON */
+ hsync = TRUE;
+ break;
+ }
+}
+
+
+void SPECReset(Z80 *z80)
+{
+ int f;
+
+ for(f=0;f<8;f++)
+ matrix[f]=0x1f;
+
+ Z80Reset(z80);
+ Z80ResetCycles(z80,0);
+
+ nmigen = FALSE;
+ hsync = FALSE;
+}
+
+
+void SPECEnableFileSystem(int enable)
+{
+ enable_filesystem=enable;
+}
+
+
+void SPECSetTape(const Z80Byte *image, int len)
+{
+ tape_image=image;
+ tape_len=len;
+}
+
+
+void SPECReconfigure(void)
+{
+ allow_save = enable_filesystem && DSSPEC_Config[DSSPEC_ALLOW_TAPE_SAVE];
+}
+
+
+void SPECSaveSnapshot(FILE *fp)
+{
+ int f;
+
+ for(f=0; f<sizeof mem; f++)
+ {
+ PUT_Byte(fp, mem[f]);
+ }
+
+ for(f=0; f<sizeof matrix; f++)
+ {
+ PUT_Byte(fp, matrix[f]);
+ }
+
+ PUT_ULong(fp, RAMBOT);
+ PUT_ULong(fp, RAMTOP);
+}
+
+
+void SPECLoadSnapshot(FILE *fp)
+{
+ int f;
+
+ for(f=0; f<sizeof mem; f++)
+ {
+ mem[f] = GET_Byte(fp);
+ }
+
+ for(f=0; f<sizeof matrix; f++)
+ {
+ matrix[f] = GET_Byte(fp);
+ }
+
+ RAMBOT = GET_ULong(fp);
+ RAMTOP = GET_ULong(fp);
+}
+
+
+/* END OF FILE */
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