/*
 * vdc-mem.c - Memory interface for the MOS 8563 (VDC) emulation.
 *
 * Written by
 *  Markus Brenner   <markus@brenner.de>
 *  Ettore Perazzoli <ettore@comm2000.it>
 *  Andreas Boose <viceteam@t-online.de>
 *  Errol Smith <strobey@users.sourceforge.net>
 *
 * This file is part of VICE, the Versatile Commodore Emulator.
 * See README for copyright notice.
 *
 *  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 2 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, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
 *  02111-1307  USA.
 *
 */

#include "vice.h"

#include <stdlib.h>
#include <string.h>

#include <stdio.h>
#include "lib.h"
#include "log.h"
#include "machine.h"
#include "maincpu.h"
#include "monitor.h"
#include "types.h"
#include "vdc-mem.h"
#include "vdc.h"
#include "vdctypes.h"
#include "vdc-draw.h"
#include "videoarch.h"
#include "vdc-resources.h"

static CLOCK vdc_status_clear_clock = 0;

/*#define REG_DEBUG*/

/* bitmask to set the unused bits in returned register values */
static const uint8_t regmask[38] = {
    0x00, 0x00, 0x00, 0x00, 0x00, 0xE0, 0x00, 0x00,
    0xFC, 0xE0, 0x80, 0xE0, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xE0,
    0x00, 0x00, 0x00, 0x00, 0x0f, 0xE0, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0xF0, 0x3F
};

static void vdc_write_data(void)
{
    int ptr;

    /* Update address.  */
    ptr = (vdc.regs[18] << 8) + vdc.regs[19];

    /* Write data byte to update address. */
    vdc_ram_store(ptr, vdc.regs[31]);
#ifdef REG_DEBUG
    log_message(vdc.log, "STORE %04i %02x", ptr,
                vdc.regs[31]);
#endif
    ptr += 1;
    vdc.regs[18] = (ptr >> 8) & 0xff;
    vdc.regs[19] = ptr & 0xff;
}


static void vdc_perform_fillcopy(void)
{
    int ptr, ptr2;
    int i;
    int blklen;

    /* Word count, # of bytes to copy */
    blklen = vdc.regs[30] ? vdc.regs[30] : 256;

    /* Update address.  */
    ptr = (vdc.regs[18] << 8) + vdc.regs[19];

    if (vdc.regs[24] & 0x80) { /* COPY flag */
        /* Block start address.  */
        ptr2 = (vdc.regs[32] << 8) + vdc.regs[33];
        for (i = 0; i < blklen; i++) {
            vdc_ram_store((ptr + i),
                vdc_ram_read(ptr2 + i));
        }
        ptr2 += blklen;
        vdc.regs[31] = vdc_ram_read(ptr2 - 1);
        vdc.regs[32] = (ptr2 >> 8) & 0xff;
        vdc.regs[33] = ptr2 & 0xff;
        /* Set the clock for when the vdc status will be clear after this operation */
        vdc_status_clear_clock = maincpu_clk + (blklen*120/100);    /* Copies take longer than fills (below) */
    } else { /* FILL */
#ifdef REG_DEBUG
        log_message(vdc.log, "Fill mem %04i, len %03i, data %02x",
                    ptr, blklen, vdc.regs[31]);
#endif
        for (i = 0; i < blklen; i++) {
            vdc_ram_store((ptr + i), vdc.regs[31]);
        }
        /* Set the clock for when the vdc status will be clear after this operation */
        vdc_status_clear_clock = maincpu_clk + (blklen*66/100);
    }

    ptr = ptr + blklen;
    vdc.regs[18] = (ptr >> 8) & 0xff;
    vdc.regs[19] = ptr & 0xff;
}


/* (re)calculate the width of each vdc character in pixels */
static void vdc_calculate_charwidth(void)
{
    if(vdc.regs[25] & 0x10) { /* double pixel a.k.a 40column mode */
        vdc.charwidth = 2 * (vdc.regs[22] >> 4);
    } else { /* 80 column mode */
        vdc.charwidth = 1 + (vdc.regs[22] >> 4);
    }
}


/* VDC interface functions. */

/* Store a value in a VDC register. */
void vdc_store(uint16_t addr, uint8_t value)
{
    uint8_t oldval;

    /* WARNING: assumes `maincpu_rmw_flag' is 0 or 1.  */
    machine_handle_pending_alarms(maincpu_rmw_flag + 1);

    /* $d600 sets the internal VDC register pointer */
    if ((addr & 1) == 0) {  /* writing to $d600   */
#ifdef REG_DEBUG
        /*log_message(vdc.log, "STORE $D600 %02x", value);*/
#endif
        vdc.update_reg = value & 0x3f;
        /* VDC ignores values of top 2 bits */
        return;
    }

    /* otherwise we are writing to $d601
    save the old register value in case we need it for reference */
    oldval = vdc.regs[vdc.update_reg];

    /* $d601 sets the vdc register indexed by the update register pointer */
    vdc.regs[vdc.update_reg] = value;

#ifdef REG_DEBUG
    switch (vdc.update_reg) {
        case 10:
        case 11:
        case 14:
        case 15:
        case 16:
        case 17:
        case 18:
        case 19:
        case 28:
        case 29:
        case 30:
        case 31:
        case 32:
        case 33:
        case 36:
        case 37:
            break;
        default:
            log_message(vdc.log, "REG %02i VAL %02x CRL:%03x BH:%03x 0:%02X 1:%02X 2:%02X 3:%02X 4:%02X 5:%02i 6:%02X 7:%02X 8:%01i 9:%02i 12:%02X 13:%02X 20:%02X 21:%02X 22:%02X 23:%02i 24:%02X 25:%02X 26:%02X 27:%02X 34:%02X 35:%02X",
                        vdc.update_reg, value,
                        vdc.raster.current_line, vdc.border_height,
                        vdc.regs[0], vdc.regs[1], vdc.regs[2], vdc.regs[3],
                        vdc.regs[4], (vdc.regs[5] & 0x1f), vdc.regs[6], vdc.regs[7],
                        vdc.regs[8] & 0x03, vdc.regs[9] & 0x1f, /* vdc.regs[10] & 0x7f, vdc.regs[11] & 0x1f,  */
                        vdc.regs[12], vdc.regs[13], /* vdc.regs[14], vdc.regs[15], */
                        /* 16, 17, 18, 19 */
                        vdc.regs[20], vdc.regs[21], vdc.regs[22], vdc.regs[23] & 0x1f,
                        vdc.regs[24], vdc.regs[25], vdc.regs[26], vdc.regs[27],
                        vdc.regs[34], vdc.regs[35]
                        );
            break;
    }

    log_message(vdc.log, "REG %02i VAL %02x", vdc.update_reg, value);
#endif

    switch (vdc.update_reg) {
        case 0:                 /* R00  Horizontal total (characters + 1) */
            if (vdc.regs[0] != oldval) {
                if (vdc.regs[0] >= 120 && vdc.regs[0] <= 127) {
                    vdc.xchars_total = vdc.regs[0] + 1;
                    vdc_calculate_xsync();
                }
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 0 Horizontal Total:%02x", vdc.xchars_total);
#endif
            break;
        case 1:                 /* R01  Horizontal characters displayed */
            if (vdc.regs[1] != oldval) {
                if (vdc.regs[1] >= 8 && vdc.regs[1] <= VDC_SCREEN_MAX_TEXTCOLS) {
                    if (vdc.screen_text_cols != vdc.regs[1]) {
                        vdc.update_geometry = 1;
                    }
                }
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 1 Horizontal Displayed:%02x", vdc.regs[1]);
#endif
            break;

        case 2:                 /* R02  Horizontal Sync Position */
            if (vdc.regs[2] != oldval) {
                vdc.update_geometry = 1;
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 2 Horizontal Sync Pos:%02x", vdc.regs[2]);
#endif
            break;

        case 3:                 /* R03  Horizontal/Vertical Sync widths */
            if ((vdc.regs[3] & 0xF0u) != (oldval & 0xF0u)) {
                vdc.update_geometry = 1;
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 3 Hor/Ver Sync Width:%02x", vdc.regs[3]);
#endif
            break;

        case 4:                 /* R04  Vertical total (character) rows */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 4 Vertical Total :%02x", vdc.regs[4]);
#endif
            break;

        case 5:                 /* R05  Vertical total line adjust */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 5 Vertical Total Fine Adjust :%02x", vdc.regs[5]);
#endif
            break;

        case 6:                 /* R06  Number of display lines on screen */
            if (vdc.regs[6] != oldval) {
                vdc.update_geometry = 1;
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 6 Vertical Displayed :%02x", vdc.regs[6]);
#endif
            break;

        case 7:                 /* R07  Vertical sync position */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 7 Vertical Sync Position :%02x", vdc.regs[7]);
#endif
            break;

        case 8:                 /* R08  Interlace and Skew */
            if ((vdc.regs[8] & 0x03) == 3)  {   /* interlace sync and video */
                vdc.interlaced = 1;
                vdc.raster.canvas->videoconfig->interlaced = 1;
            } else if ((vdc.regs[8] & 0x03) == 1)  {   /* interlace sync */
                /* we don't set vdc.interlaced here because in interlace sync the fields are identical,
                   they are just offset, so the VDC behaviour doesn't change, only the renderer */
                vdc.interlaced = 0;
                vdc.raster.canvas->videoconfig->interlaced = 1;
            } else {    /* 0x00 or 0x02 are non-interlaced */
                vdc.interlaced = 0;
                vdc.raster.canvas->videoconfig->interlaced = 0;
            }
            /* vdc.update_geometry = 1; */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 8 Interlace:%02x", vdc.regs[8]);
#endif
            break;

        case 9:                 /* R09  Rasters between two display lines */
            if ((vdc.regs[9] & 0x1fu) != (oldval & 0x1fu)) {
                vdc.raster_ycounter_max = vdc.regs[9] & 0x1f;
                if (vdc.raster_ycounter_max < 16) {
                    vdc.bytes_per_char = 16;
                } else {
                    vdc.bytes_per_char = 32;
                }
            }
            /* set the attribute offset to 3 if reg[9] transitions from 0 on the last row to
               correctly (?) emulate the 8x1 colour cell VDC trick in RFOVDC FLI picture */
            if (((oldval & 0x1fu) == 0) && (vdc.row_counter == (vdc.regs[6]-1))) {
                vdc.attribute_offset = 3;
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "Character Total Vertical %i", vdc.regs[9]);
#endif
            break;

        case 10:                /* R10  Cursor Mode, Start Scan */
            break;

        case 11:                /* R11  Cursor End Scan */
            break;

        case 12:                /* R12  Display Start Address hi */
        case 13:                /* R13  Display Start Address lo */
            /* Screen address will be taken after last displayed line.  */
#ifdef REG_DEBUG
            log_message(vdc.log, "Update screen_adr: %x.", vdc.screen_adr);
#endif
            break;

        case 14:
        case 15:                /* R14-5 Cursor location HI/LO */
            vdc.crsrpos = (vdc.regs[14] << 8) | vdc.regs[15];
            break;

        case 16:                /* R16/17 Light Pen hi/lo */
        case 17:
            /* lightpen registers are read-only, so put the old value back */
            vdc.regs[vdc.update_reg] = oldval;
            break;

        case 18:                /* R18/19 Update Address hi/lo */
        case 19:
            vdc.update_adr = ((vdc.regs[18] << 8) | vdc.regs[19]);
            /* writing to 18/19 forces the vdc to go read its memory, which takes a while */
            if (vdc.display_enable) {
                vdc_status_clear_clock = maincpu_clk + 43;  /* The VDC is 'busier' when in the active display area */
            } else {
                vdc_status_clear_clock = maincpu_clk + 4;   /* And less busy in the top/bottom border */
            }
            break;

        case 20:                /* R20/21 Attribute Start Address hi/lo */
        case 21:
            /* Attribute address will be taken after last displayed line.  */
#ifdef REG_DEBUG
            log_message(vdc.log, "Update attribute_adr: %x.", vdc.attribute_adr);
#endif
            break;

        case 22:                /* R22 Character Horizontal Size Control */
            /* TODO - changes to this register are real time, so need raster_changes() type call, but why bother... */
            vdc_calculate_charwidth();
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 22 only partially supported!");
#endif
            break;

        case 23:                /* R23 Vert. Character Pxl Spc */
#ifdef REG_DEBUG
            log_message(vdc.log, "Vert. Character Pxl Spc %i.",
                        vdc.regs[23] & 0x1f);
#endif
            break;

        case 24:
            if (vdc.regs[24] & 0x20) {
                vdc.attribute_blink = vdc.frame_counter & 16;
            } else {
                vdc.attribute_blink = vdc.frame_counter & 8;
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "Vertical Smooth Scroll %i.", vdc.regs[24] & 0x1f);
            log_message(vdc.log, "Blink frequency: %s.",
                        (vdc.regs[24] & 0x20) ? "1/32" : "1/16");
            log_message(vdc.log, "Screen mode: %s.",
                        (vdc.regs[24] & 0x40) ? "reverse" : "normal");
#endif
            break;

        case 25:
            if ((vdc.regs[25] & 0x0Fu) != (oldval & 0x0Fu)) {
                /* Horizontal smooth scroll */
#ifdef ALLOW_UNALIGNED_ACCESS
                /* Smooth scroll behaviour differs between VDC versions:
                Incrementing HSS always moves the screen contents to the right,
                but in v0 VDC, the left border moves to the right as well(!),
                which makes scrolling almost totally useless.
                Also, v0 VDC has another, even more serious bug:
                if xsmooth == (vdc.regs[22] >> 4), pixel data of leftmost char
                is missing (inside border?) so pixel data and attributes are out
                of sync! This also affects the hardware cursor, which appears to
                be located one char to the right.
                In v1/v2 VDC, the bugs are fixed: the border is fixed so only
                the rightmost pixel of the leftmost char is visible, which is
                why (vdc.regs[22] >> 4) has to be used as xsmooth init value. */
                if (vdc.revision == VDC_REVISION_0) {
                    /* v0 VDC, incrementing HSS moves border and screen to the right */
                    vdc.v0xscroll = (vdc.regs[25] & 0x0F);
                    vdc.xsmooth = (vdc.regs[22] >> 4) & 0x0F;
                } else {
                    /* v1/2 VDC, incrementing HSS moves screen to the right */
                    vdc.v0xscroll = 0;
                    vdc.xsmooth = (vdc.regs[25] & 0x0F);
                }
                vdc.border_width = vdc.iborder_width + vdc.v0xscroll;
                vdc.raster.xsmooth = 0;
                /* Hack to get the line redrawn because we are not actually using the xsmooth in raster
                (so the xsmooth color is irrelevant, but changing it still forces a repaint of the line) */
                vdc.raster.xsmooth_color++;
#else
                vdc.xsmooth = (vdc.regs[22] >> 4) - ((vdc.regs[25] & 0x10) ? 1 : 0);
                vdc.raster.xsmooth = 0;
#endif
            }
            if ((vdc.regs[25] & 0x10u) != (oldval & 0x10u)) {
                /* Double-Pixel Mode */
                vdc.update_geometry = 1;
            }
            vdc_calculate_charwidth();
#ifdef REG_DEBUG
            log_message(vdc.log, "Video mode: %s.",
                        (vdc.regs[25] & 0x80) ? "bitmap" : "text");
            log_message(vdc.log, "Color source: %s.",
                        (vdc.regs[25] & 0x40) ? "attribute space" : "register 26");
            if (vdc.regs[25] & 0x20) {
                log_message(vdc.log, "Semi-Graphics Mode");
            }
            if (vdc.regs[25] & 0x10) {
                log_message(vdc.log, "Double-Pixel Mode unsupported!");
            }
#endif
            break;

        case 26:
            /* TODO - figure out if this was really needed. Doesn't seem to make a difference.
                Original Comment: repaint if something changes and we are not in graphics attribute mode */
            /* if ((vdc.regs[26] != oldval) && ((vdc.regs[25] & 0xC0) != 0xC0)) {
                vdc.force_repaint = 1;
            }   */
            if ((vdc.regs[26] & 0x0Fu) != (oldval & 0x0Fu)) {
                /* Background colour changes */
                /* TODO - calculate a real current horizontal raster position for this call (2nd value) */
                /* based on blacky_stardust calculations, calculating current_x_pixel should be like:
                current_x_pixel = pixels_per_line / (vdc.xsync_increment >> 16) * (current_cycle - vdc_line_start) */
                /* int current_x_pixel = 0; */
                /*        if (((vdc.xsync_increment * (maincpu_clk - vdc.vdc_line_start)) >> 16) != 0) {
                            current_x_pixel = (long long) (vdc.regs[0] + 1) * ((vdc.regs[22] >> 4) + 1) / ((vdc.xsync_increment * (maincpu_clk - vdc.vdc_line_start)) >> 16);
                        }
            */
                /* TODO get rid of this when it works properly */
                /*     fprintf(stderr, "current_x_pixel=%1i\n", current_x_pixel);
                     raster_changes_border_add_int(&vdc.raster,
                     current_x_pixel,
                     (int*)&vdc.raster.border_color,
                     (vdc.regs[26] & 0x0F));
                     vdc.raster.xsmooth_color = vdc.regs[26] & 0x0F; */
                /* Set the xsmooth area too for the 0-7pixel gap between border & foreground */

                vdc.raster.border_color = (vdc.regs[26] & 0x0F);
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "Color register %x.", vdc.regs[26]);
#endif
            break;

        case 27:                /* R27  Row/Adrs. Increment */
            /* We need to redraw the current line if this changes,
            as cache will be wrong. Uses xsmooth_color hack (see reg 25) */
            vdc.raster.xsmooth_color++;
            vdc.skip_after_line = vdc.regs[27];
            /* emulate quirk of v0, where 0 means 0 and all other values mean one more! */
            if ((vdc.revision == VDC_REVISION_0) && (vdc.regs[27])) {
                vdc.skip_after_line++;
            }
#ifdef REG_DEBUG
            log_message(vdc.log, "Row/Adrs. Increment %i.", vdc.regs[27]);
#endif
            break;

        case 28:                /* Character pattern address and memory type */
            /* FIXME reg28 bit 4 sets RAM addressing. it does *not* show how much ram is installed */
            vdc.chargen_adr = ((vdc.regs[28] << 8) & 0xe000);
#ifdef REG_DEBUG
            log_message(vdc.log, "Update chargen_adr: %x.", vdc.chargen_adr);
#endif
            break;

        case 30:                /* Word Count + initiate fill or copy */
            vdc_perform_fillcopy();
            break;

        case 31:                /* Data for memory write */
            vdc_write_data();
            /* Set the clock for when the vdc status will be clear after this operation */
            if (vdc.display_enable) {
                vdc_status_clear_clock = maincpu_clk + 43;  /* The VDC is 'busier' when in the active display area */
            } else {
                vdc_status_clear_clock = maincpu_clk + 4;   /* And less busy in the top/bottom border */
            }
            break;

        case 32:                /* R32/33 Block Start Address hi/lo */
        case 33:
            break;

        case 34:                /* R34  Display Enable Begin */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 34 unsupported!");
#endif
            break;

        case 35:                /* R35  Display Enable End */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 35 unsupported!");
#endif
            break;

        case 36:                /* R36  DRAM Refresh Rate */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 36 unsupported!");
#endif
            break;

        case 37:                /* R37  Vertical/Horizontal Sync Polarity on 8568 (128DCR) only */
#ifdef REG_DEBUG
            log_message(vdc.log, "REG 37 unsupported!");
#endif
            break;
    }
}


uint8_t vdc_read(uint16_t addr)
{
    uint8_t retval;
    int ptr;

    machine_handle_pending_alarms(0);

    if (addr & 1) { /* read $d601 (and mirrors $d603/5/7....$d6ff)  */
        /*log_message(vdc.log, "read: addr = %x", addr);*/

        if (vdc.update_reg == 31) {
            retval = vdc_ram_read((vdc.regs[18] << 8) + vdc.regs[19]);
            ptr = (1 + vdc.regs[19] + (vdc.regs[18] << 8));
            vdc.regs[18] = (ptr >> 8) & 0xff;
            vdc.regs[19] = ptr & 0xff;
            /* Set the clock for when the vdc status will be clear after this operation */
            if (vdc.display_enable) {
                vdc_status_clear_clock = maincpu_clk + 43;  /* The VDC is 'busier' when in the active display area */
            } else {
                vdc_status_clear_clock = maincpu_clk + 4;   /* And less busy in the top/bottom border */
            }
            return retval;
        }

        /* reset light pen flag if either light pen position register is read */
        if (vdc.update_reg == 16 || vdc.update_reg == 17) {
            vdc.light_pen.triggered = 0;
        }

        if (vdc.update_reg < 38) {
            return (vdc.regs[vdc.update_reg] | regmask[vdc.update_reg]);
        }

        return 0xff; /* return 0xFF for invalid register numbers */
    } else { /* read $d600 (and mirrors $d602/4/6....$d6fe) */
        retval = vdc.revision;

        /* Status ($80) is set when the VDC is ready for the next register access.
           we use an (approximate) timer hack to see if it is ready yet. */
        if (maincpu_clk > vdc_status_clear_clock) {
            retval |= 0x80;
        } else if (maincpu_clk + 10000 < vdc_status_clear_clock) {
            /* safety check in case maincpu_clk overflows */
            vdc_status_clear_clock = maincpu_clk;
        }

        /* Emulate lightpen flag. */
        if (vdc.light_pen.triggered) {
            retval |= 0x40;
        }

        /* Emulate VBLANK bit. If the bit is set, we are in the top or bottom border. If zero we are in the active area.
           Confusingly this has nothing to do with vertical retrace or vertical sync pulse, despite the name & what documentation says. */
        if (!vdc.display_enable) {
            retval |= 0x20;
        }

        return retval;
    }
}


uint8_t vdc_peek(uint16_t addr)    /* No sidefx read of external VDC registers */
{
    if (addr & 1) { /* read $d601 (and mirrors $d603/5/7....$d6ff)  */

        /* Read VDCs RAM without incrementing the pointer */
        if (vdc.update_reg == 31) {
            return vdc_ram_read((vdc.regs[18] << 8) + vdc.regs[19]);
        }

        /* Make sure light pen flag is not altered if either light pen position register is read */
        if (vdc.update_reg == 16 || vdc.update_reg == 17) {
            return (vdc.regs[vdc.update_reg]);
        }

        return vdc_read(addr);  /* Use existing read function for rest */
    } else {    /* read $d600 (and mirrors $d602/4/6....$d6fe) */
        /* read of $d600 is non destructive, so just use the value calculated in vdc_read() */
        return vdc_read(addr);
    }
}

/* address translation function for a 16KB VDC in 64KB mode, used by read/write functions below */
static uint16_t vdc_16k_to_64k_map(uint16_t address)
{
    uint16_t new_address = address & 0x80ff;
    uint16_t tmp = address & 0x3f00;
    uint16_t low_bit = address & 0x0100;

    tmp <<= 1;
    tmp |= low_bit;
    new_address |= tmp;
    return new_address;
}

/* address translation function for a 64KB VDC in 16KB mode, used by read/write functions below */
static uint16_t vdc_64k_to_16k_map(uint16_t address)
{
    uint16_t new_address = address & 0x00ff;
    uint16_t tmp = address & 0x7e00;

    tmp >>= 1;
    new_address |= tmp;
    return new_address;
}

uint8_t vdc_ram_read(uint16_t addr)
{   /* perform necessary address translations when memory configuration doesn't match memory addressing */
    if (vdc.regs[28] & 0x10) {
        if (vdc_resources.vdc_64kb_expansion) {
            /* 64KB addressing, 4464 chips 64KB */
            return vdc.ram[addr];
        } else {
            /* 64KB addressing, 4416 chips 16KB */
            return vdc.ram[vdc_64k_to_16k_map(addr)];
        }
    } else {
        if (vdc_resources.vdc_64kb_expansion) {
            /* 16KB addressing, 4464 chips 64KB */
            return vdc.ram[vdc_16k_to_64k_map(addr)];
        } else {
            /* 16KB addressing, 4416 chips 16KB */
            return vdc.ram[addr & 0x3fff];
        }
    }
}

void vdc_ram_store(uint16_t addr, uint8_t value)
{   /* as above but for storing to VDC ram with appropriate address translation*/
    if (vdc.regs[28] & 0x10) {
        if (vdc_resources.vdc_64kb_expansion) {
            /* 64KB addressing, 4464 chips 64KB */
            vdc.ram[addr] = value;
        } else {
            /* 64KB addressing, 4416 chips 16KB */
            vdc.ram[vdc_64k_to_16k_map(addr)] = value;
        }
    } else {
        if (vdc_resources.vdc_64kb_expansion) {
            /* 16KB addressing, 4464 chips 64KB */
            vdc.ram[vdc_16k_to_64k_map(addr)] = value;
        } else {
            /* 16KB addressing, 4416 chips 16KB */
            vdc.ram[addr & 0x3fff] = value;
        }
    }
}


int vdc_dump(void)
{
    unsigned int r, c, regnum=0, location, size;

    /* Dump the internal VDC registers */
    mon_out("VDC Internal Registers:\n");
    for (r = 0; r < 3; r++) {
        mon_out("%02x: ", regnum);
        for (c = 0; c < 16; c++) {
            if (regnum <= 37) {
                mon_out("%02x ", (unsigned int)(vdc.regs[regnum] | regmask[regnum]));
            }
            regnum++;
            if ((c & 3) == 3) {
                mon_out(" ");
            }
        }
        mon_out("\n");
    }
    mon_out("\nVDC Revision   : %u", vdc.revision);
    mon_out("\nVertical Blanking Period: ");
    mon_out(((vdc.raster.current_line <= vdc.border_height) || (vdc.raster.current_line > (vdc.border_height + vdc.screen_ypix))) ? "Yes" : "No");
    mon_out("\nLight Pen Triggered: ");
    mon_out(vdc.light_pen.triggered ? "Yes" : "No");
    mon_out("\nStatus         : ");
    mon_out(maincpu_clk > vdc_status_clear_clock ? "Ready" : "Busy");
    mon_out("\nActive Register: %d", vdc.update_reg);
    mon_out("\nAddress Mask   : $%04x",
            (unsigned int)vdc.vdc_address_mask);
    mon_out("\nMemory Address : $%04x",
            (unsigned int)((vdc.regs[18] << 8) + vdc.regs[19]));
    mon_out("\nBlockCopySource: $%04x",
            (unsigned int)((vdc.regs[32] << 8) + vdc.regs[33]));
    mon_out("\nDisplay Mode   : ");
    mon_out(vdc.regs[25] & 0x80 ? "Bitmap" : "Text");
    mon_out(vdc.regs[25] & 0x40 ? " & Attributes" : ", no Attributes");
    mon_out(vdc.regs[25] & 0x20 ? ", Semigraphic" : "");
    mon_out(vdc.regs[24] & 0x40 ? ", Reverse" : "");
    if ((vdc.regs[8] & 0x03) == 3)  {   /* interlace sync and video */
        mon_out(", Interlaced Sync & Video");
    } else if ((vdc.regs[8] & 0x03) == 1)  {   /* interlace sync */
        mon_out(", Interlaced Sync");
    } else {    /* 0x00 or 0x02 are non-interlaced */
        mon_out(", Non-Interlaced");
    }
    if (vdc.regs[25] & 0x10) { /* double pixel mode aka 40column mode */
        mon_out(", Pixel Double");
        mon_out("\nScreen Size    : %d x %d chars", vdc.regs[1], vdc.regs[6]);
        mon_out("\nCharacter Size : %d x %d pixels (%d x %d visible)", vdc.regs[22] >> 4, (vdc.regs[9] & 0x1f) + 1, (vdc.regs[22] & 0x0f) + 1, (vdc.regs[23] & 0x1f) + 1);
        mon_out("\nActive Pixels  : %d x %d", vdc.regs[1] * (vdc.regs[22] >> 4), vdc.regs[6] * ((vdc.regs[9] & 0x1f) + 1));
        mon_out("\nFrame inc. Sync: %d x %d @ %f fps", (vdc.regs[0] + 1) * (vdc.regs[22] >> 4), (vdc.regs[4] + 1) * ((vdc.regs[9] & 0x1f) + 1) + (vdc.regs[5] & 0x1f),
                                    VDC_DOT_CLOCK / (2 * (vdc.regs[0] + 1) * (vdc.regs[22] >> 4) * ((vdc.regs[4] + 1) * ((vdc.regs[9] & 0x1f) + 1) + (vdc.regs[5] & 0x1f))));
    } else {
        mon_out("\nScreen Size    : %d x %d chars", vdc.regs[1], vdc.regs[6]);
        mon_out("\nCharacter Size : %d x %d pixels (%d x %d visible)", (vdc.regs[22] >> 4) + 1, (vdc.regs[9] & 0x1f) + 1, (vdc.regs[22] & 0x0f) + 1, (vdc.regs[23] & 0x1f) + 1);
        mon_out("\nActive Pixels  : %d x %d", vdc.regs[1] * ((vdc.regs[22] >> 4) + 1), vdc.regs[6] * ((vdc.regs[9] & 0x1f) + 1));
        mon_out("\nFrame inc. Sync: %d x %d @ %f fps", (vdc.regs[0] + 1) * ((vdc.regs[22] >> 4) + 1), (vdc.regs[4] + 1) * ((vdc.regs[9] & 0x1f) + 1) + (vdc.regs[5] & 0x1f),
                                    VDC_DOT_CLOCK / ((vdc.regs[0] + 1) * ((vdc.regs[22] >> 4) + 1) * ((vdc.regs[4] + 1) * ((vdc.regs[9] & 0x1f) + 1) + (vdc.regs[5] & 0x1f))));
    }

    location = ((vdc.regs[12] << 8) + vdc.regs[13]);
    if (vdc.regs[25] & 0x80 ) {
        size = vdc.regs[1] * vdc.regs[6] * ((vdc.regs[9] & 0x1f) + 1);  /* bitmap size */
    } else {
        size = vdc.regs[1] * vdc.regs[6];   /* text mode size */
    }
    mon_out("\nScreen Memory  : $%04x-$%04x (Size $%04x)", location, (location + size - 1), size);

    location = ((vdc.regs[20] << 8) + vdc.regs[21]);
    size = vdc.regs[1] * vdc.regs[6];
    mon_out("\nAttrib Memory  : $%04x-$%04x (Size $%04x)", location, (location + size - 1), size);

    location = ((vdc.regs[28] & 0xE0) << 8);
    size = 0x200 * vdc.bytes_per_char; /* 0x2000 or 0x4000, depending on character height */
    mon_out("\nCharset Memory : $%04x-$%04x (Size $%04x)", location, (location + size - 1), size);

    mon_out("\nCursor Address : $%04x",
            (unsigned int)(((vdc.regs[14] << 8) + vdc.regs[15])));
    mon_out("\n");
    return 0;
}