pio.c

/*
    pio.c --
    I/O chip and peripheral emulation.
*/
#include "shared.h"

io_state io_lut[2][256];
io_state *io_current;

void pio_init(void)
{
    int i, j;

    /* Make pin state LUT */
    for(j = 0; j < 2; j++)
    {
        for(i = 0; i < 0x100; i++)
        {
            /* Common control: pin direction */
            io_lut[j][i].tr_dir[0]   = (i & 0x01) ? PIN_DIR_IN : PIN_DIR_OUT;
            io_lut[j][i].th_dir[0]   = (i & 0x02) ? PIN_DIR_IN : PIN_DIR_OUT;
            io_lut[j][i].tr_dir[1]   = (i & 0x04) ? PIN_DIR_IN : PIN_DIR_OUT;
            io_lut[j][i].th_dir[1]   = (i & 0x08) ? PIN_DIR_IN : PIN_DIR_OUT; 

            if(j == 1)
            {
                /* Programmable output state (Export machines only) */
                io_lut[j][i].tr_level[0] = (i & 0x01) ? PIN_LVL_HI : (i & 0x10) ? PIN_LVL_HI : PIN_LVL_LO;
                io_lut[j][i].th_level[0] = (i & 0x02) ? PIN_LVL_HI : (i & 0x20) ? PIN_LVL_HI : PIN_LVL_LO;
                io_lut[j][i].tr_level[1] = (i & 0x04) ? PIN_LVL_HI : (i & 0x40) ? PIN_LVL_HI : PIN_LVL_LO;
                io_lut[j][i].th_level[1] = (i & 0x08) ? PIN_LVL_HI : (i & 0x80) ? PIN_LVL_HI : PIN_LVL_LO;
            }
            else
            {
                /* Fixed output state (Domestic machines only) */
                io_lut[j][i].tr_level[0] = (i & 0x01) ? PIN_LVL_HI : PIN_LVL_LO;
                io_lut[j][i].th_level[0] = (i & 0x02) ? PIN_LVL_HI : PIN_LVL_LO;
                io_lut[j][i].tr_level[1] = (i & 0x04) ? PIN_LVL_HI : PIN_LVL_LO;
                io_lut[j][i].th_level[1] = (i & 0x08) ? PIN_LVL_HI : PIN_LVL_LO;
            }
        }
    }

    // hack dos code doesn't call system_reset
    pio_reset();
}


void pio_reset(void)
{
    /* GG SIO power-on defaults */
    sms.sio.pdr     = 0x7F;
    sms.sio.ddr     = 0xFF;
    sms.sio.txdata  = 0x00;
    sms.sio.rxdata  = 0xFF;
    sms.sio.sctrl   = 0x00;

    /* SMS I/O power-on defaults */
    ioctrl_w(0xFF);
}


void pio_shutdown(void)
{
    /* Nothing to do */
}


void system_assign_device(int port, int type)
{
    sms.device[port].type = type;
}

void ioctrl_w(uint8 data)
{
    sms.ioctrl = data;
    io_current = &io_lut[sms.territory][data];
}

uint8 device_r(int offset)
{
    uint8 temp = 0x7F;

    switch(sms.device[offset].type)
    {
        case DEVICE_NONE:
            break;
        case DEVICE_PAD2B:
            break;
        case DEVICE_PADDLE:
            break;
    }

    return temp;
}

uint8 input_r(int offset)
{
    uint8 temp = 0xFF;

    /*
        If I/O chip is disabled, reads return last byte of instruction that
        read the I/O port.
    */
    if(sms.memctrl & 0x04)
        return z80_read_unmapped();

    offset &= 1;
    if(offset == 0)
    {
        /* Input port #0 */

        if(input.pad[0] & INPUT_UP)         temp &= ~0x01; /* D0 */
        if(input.pad[0] & INPUT_DOWN)       temp &= ~0x02; /* D1 */
        if(input.pad[0] & INPUT_LEFT)       temp &= ~0x04; /* D2 */
        if(input.pad[0] & INPUT_RIGHT)      temp &= ~0x08; /* D3 */
        if(input.pad[0] & INPUT_BUTTON2)    temp &= ~0x10; /* TL */
        if(input.pad[0] & INPUT_BUTTON1)    temp &= ~0x20; /* TR */

        if(sms.console == CONSOLE_GG)
        {
            uint8 state = sio_r(0x01);
            temp = (temp & 0x3F) | (state & 0x03) << 6; /* Insert D1,D0 */
        }
        else
        {
            if(input.pad[1] & INPUT_UP)     temp &= ~0x40; /* D0 */
            if(input.pad[1] & INPUT_DOWN)   temp &= ~0x80; /* D1 */
        }

        /* Adjust TR state if it is an output */
        if(io_current->tr_dir[0] == PIN_DIR_OUT) {
            temp &= ~0x20;
            temp |= (io_current->tr_level[0] == PIN_LVL_HI) ? 0x20 : 0x00;
        }
    }
    else
    {
        /* Input port #1 */
        if(sms.console == CONSOLE_GG)
        {
            uint8 state = sio_r(0x01);
            temp = (temp & 0xF0) | ((state & 0x3C) >> 2); /* Insert TR,TL,D3,D2 */
            temp = (temp & 0x7F) | ((state & 0x40) << 1); /* Insert TH */
        }
        else
        {
            if(input.pad[1] & INPUT_LEFT)       temp &= ~0x01; /* D2 */
            if(input.pad[1] & INPUT_RIGHT)      temp &= ~0x02; /* D3 */
            if(input.pad[1] & INPUT_BUTTON2)    temp &= ~0x04; /* TL */
            if(input.pad[1] & INPUT_BUTTON1)    temp &= ~0x08; /* TR */

            /* Adjust TR state if it is an output */
            if(io_current->tr_dir[1] == PIN_DIR_OUT) {
                temp &= ~0x08;
                temp |= (io_current->tr_level[1] == PIN_LVL_HI) ? 0x08 : 0x00;
            }
        
            /* Adjust TH state if it is an output */
            if(io_current->th_dir[1] == PIN_DIR_OUT) {
                temp &= ~0x80;
                temp |= (io_current->th_level[1] == PIN_LVL_HI) ? 0x80 : 0x00;
            }

            if(input.system & INPUT_RESET)  temp &= ~0x10;
        }

        /* /CONT fixed at '1' for SMS/SMS2/GG */
        /* /CONT fixed at '0' for GEN/MD */
        if(IS_MD) temp &= ~0x20;

        /* Adjust TH state if it is an output */
        if(io_current->th_dir[0] == PIN_DIR_OUT) {
            temp &= ~0x40;
            temp |= (io_current->th_level[0] == PIN_LVL_HI) ? 0x40 : 0x00;
        }
    }
    return temp;
}

uint8 sio_r(int offset)
{
    uint8 temp;

    switch(offset & 0xFF)
    {
        case 0: /* Input port #2 */
            temp = 0xE0;
            if(input.system & INPUT_START)          temp &= ~0x80;
            if(sms.territory == TERRITORY_DOMESTIC) temp &= ~0x40;
            if(sms.display == DISPLAY_NTSC)         temp &= ~0x20;
            return temp;

        case 1: /* Parallel data register */
            temp = 0x00;
            temp |= (sms.sio.ddr & 0x01) ? 0x01 : (sms.sio.pdr & 0x01);
            temp |= (sms.sio.ddr & 0x02) ? 0x02 : (sms.sio.pdr & 0x02);
            temp |= (sms.sio.ddr & 0x04) ? 0x04 : (sms.sio.pdr & 0x04);
            temp |= (sms.sio.ddr & 0x08) ? 0x08 : (sms.sio.pdr & 0x08);
            temp |= (sms.sio.ddr & 0x10) ? 0x10 : (sms.sio.pdr & 0x10);
            temp |= (sms.sio.ddr & 0x20) ? 0x20 : (sms.sio.pdr & 0x20);
            temp |= (sms.sio.ddr & 0x40) ? 0x40 : (sms.sio.pdr & 0x40);
            temp |= (sms.sio.pdr & 0x80);
            return temp;

        case 2: /* Data direction register and NMI enable */
            return sms.sio.ddr;

        case 3: /* Transmit data buffer */
            return sms.sio.txdata;

        case 4: /* Receive data buffer */
            return sms.sio.rxdata;

        case 5: /* Serial control */
            return sms.sio.sctrl;

        case 6: /* Stereo sound control */
            return 0xFF;
    }

    /* Just to please compiler */
    return -1;
}

void sio_w(int offset, int data)
{
    switch(offset & 0xFF)
    {
        case 0: /* Input port #2 (read-only) */
            return;

        case 1: /* Parallel data register */
            sms.sio.pdr = data;
            return;

        case 2: /* Data direction register and NMI enable */
            sms.sio.ddr = data;
            return;

        case 3: /* Transmit data buffer */
            sms.sio.txdata = data;
            return;

        case 4: /* Receive data buffer */
            return;

        case 5: /* Serial control */
            sms.sio.sctrl = data & 0xF8;
            return;
        
        case 6: /* Stereo output control */
            psg_stereo_w(data);
            return;
    }
}