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i8275x: Fixed DMA burst length. It is specified in received characters, not character clocks. [Curt Coder]

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This commit is contained in:
Curt Coder 2014-04-30 05:11:05 +00:00
parent bd52970133
commit e86661d2a1
2 changed files with 29 additions and 35 deletions
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61
src/emu/video/i8275x.c
View File

@ -13,6 +13,7 @@
TODO:
- character attributes
- double spaced rows
*/
@ -132,7 +133,6 @@ void i8275x_device::device_start()
// allocate timers
m_hrtc_on_timer = timer_alloc(TIMER_HRTC_ON);
m_drq_on_timer = timer_alloc(TIMER_DRQ_ON);
m_drq_off_timer = timer_alloc(TIMER_DRQ_OFF);
m_scanline_timer = timer_alloc(TIMER_SCANLINE);
// state saving
@ -185,28 +185,6 @@ void i8275x_device::device_timer(emu_timer &timer, device_timer_id id, int param
case TIMER_DRQ_ON:
//if (LOG) logerror("I8275 '%s' y %u x %u DRQ 1\n", tag(), y, x);
m_write_drq(1);
m_drq_off_timer->adjust(clocks_to_attotime(DMA_BURST_COUNT));
break;
case TIMER_DRQ_OFF:
if (m_buffer_idx == 0)
{
m_status |= ST_DU;
m_du = true;
//if (LOG) logerror("I8275 '%s' y %u x %u DRQ 0\n", tag(), y, x);
m_write_drq(0);
}
else if (m_buffer_idx == CHARACTERS_PER_ROW)
{
//if (LOG) logerror("I8275 '%s' y %u x %u DRQ 0\n", tag(), y, x);
m_write_drq(0);
}
else if (DMA_BURST_SPACE > 0)
{
//if (LOG) logerror("I8275 '%s' y %u x %u DRQ 0\n", tag(), y, x);
m_write_drq(0);
m_drq_on_timer->adjust(clocks_to_attotime(DMA_BURST_SPACE));
}
break;
case TIMER_SCANLINE:
@ -252,12 +230,20 @@ void i8275x_device::device_timer(emu_timer &timer, device_timer_id id, int param
if (lc == 0)
{
if ((m_scanline < m_vrtc_scanline - SCANLINES_PER_ROW) && (m_buffer_idx < CHARACTERS_PER_ROW) && !m_du)
{
m_status |= ST_DU;
m_du = true;
//if (LOG) logerror("I8275 '%s' y %u x %u DMA Underrun\n", tag(), y, x);
m_write_drq(0);
}
// swap line buffers
m_buffer_dma = !m_buffer_dma;
m_buffer_idx = 0;
m_fifo_idx = 0;
if (!m_du && ((m_scanline < m_vrtc_scanline - SCANLINES_PER_ROW) || (m_scanline == m_vrtc_drq_scanline)))
if ((!m_du && (m_scanline < m_vrtc_scanline - SCANLINES_PER_ROW)) || (m_scanline == m_vrtc_drq_scanline))
{
// start DMA burst
m_drq_on_timer->adjust(clocks_to_attotime(DMA_BURST_SPACE));
@ -266,11 +252,7 @@ void i8275x_device::device_timer(emu_timer &timer, device_timer_id id, int param
if (m_scanline < m_vrtc_scanline)
{
if (OFFSET_LINE_COUNTER)
{
lc = (lc - 1) & 0x0f;
}
int line_counter = OFFSET_LINE_COUNTER ? ((lc - 1) % SCANLINES_PER_ROW) : lc;
for (int sx = 0; sx < CHARACTERS_PER_ROW; sx++)
{
@ -339,7 +321,7 @@ void i8275x_device::device_timer(emu_timer &timer, device_timer_id id, int param
m_display_cb(m_bitmap,
sx * m_hpixels_per_column, // x position on screen of starting point
m_scanline, // y position on screen
lc, // current line of char
line_counter, // current line of char
(data & 0x7f), // char code to be displayed
m_lineattr, // line attribute code
lten | m_lten, // light enable signal
@ -411,6 +393,7 @@ WRITE8_MEMBER( i8275x_device::write )
m_status &= ~ST_IE;
if (LOG) logerror("I8275 '%s' IRQ 0\n", tag());
m_write_irq(CLEAR_LINE);
m_write_drq(0);
m_param_idx = REG_SCN1;
m_param_end = REG_SCN4;
@ -479,7 +462,11 @@ WRITE8_MEMBER( i8275x_device::write )
WRITE8_MEMBER( i8275x_device::dack_w )
{
//if (LOG) logerror("DACK write %02x %u\n", data, m_buffer_idx);
//int y = m_screen->vpos();
//int x = m_screen->hpos();
//if (LOG) logerror("I8275 '%s' y %u x %u DACK %04x:%02x %u\n", tag(), y, x, offset, data, m_buffer_idx);
m_write_drq(0);
if (m_fifo_next)
{
@ -504,7 +491,15 @@ WRITE8_MEMBER( i8275x_device::dack_w )
if (m_buffer_idx == CHARACTERS_PER_ROW)
{
m_drq_off_timer->adjust(attotime::zero);
// stop DMA
}
else if (!(m_buffer_idx % DMA_BURST_COUNT))
{
m_drq_on_timer->adjust(clocks_to_attotime(DMA_BURST_SPACE));
}
else
{
m_drq_on_timer->adjust(attotime::zero);
}
}
}
@ -572,5 +567,7 @@ void i8275x_device::recompute_parameters()
m_vrtc_scanline = CHARACTER_ROWS_PER_FRAME * SCANLINES_PER_ROW;
m_vrtc_drq_scanline = vert_pix_total - SCANLINES_PER_ROW;
if (LOG) logerror("irq_y %u vrtc_y %u drq_y %u\n", m_irq_scanline, m_vrtc_scanline, m_vrtc_drq_scanline);
m_scanline_timer->adjust(m_screen->time_until_pos(0, 0), 0, m_screen->scan_period());
}

3
src/emu/video/i8275x.h
View File

@ -68,7 +68,6 @@
//**************************************************************************
// TYPE DEFINITIONS
//**************************************************************************
@ -114,7 +113,6 @@ protected:
{
TIMER_HRTC_ON,
TIMER_DRQ_ON,
TIMER_DRQ_OFF,
TIMER_SCANLINE
};
@ -212,7 +210,6 @@ protected:
// timers
emu_timer *m_hrtc_on_timer;
emu_timer *m_drq_on_timer;
emu_timer *m_drq_off_timer;
emu_timer *m_scanline_timer;
};