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(MESS) a7800.c: Fixed DMA regarding startup, shutdown and cycle stealing which fixes numerous recorded MAMETester bugs. Bug fixed and fine tuned the DMA timing. Corrected RIOT timing [Mike Saarna]

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This commit is contained in:
Scott Stone 2014-03-26 03:41:11 +00:00
parent 35a825bb38
commit 233b795c21
2 changed files with 14 additions and 5 deletions
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4
src/mess/drivers/a7800.c
View File

@ -80,6 +80,8 @@
2014/02/15 Robert Tuccitto Added more details and clarification
regarding the potentiometer.
2014/03/25 Mike Saarna Fixed Riot Timer
***************************************************************************/
#include "emu.h"
@ -1047,7 +1049,7 @@ static MACHINE_CONFIG_START( a7800_ntsc, a7800_state )
MCFG_SOUND_ROUTE(ALL_OUTPUTS, "mono", 1.00)
/* devices */
MCFG_RIOT6532_ADD("riot", A7800_NTSC_Y1/12, a7800_r6532_interface)
MCFG_RIOT6532_ADD("riot", A7800_NTSC_Y1/8, a7800_r6532_interface)
MCFG_CARTSLOT_ADD("cart")
MCFG_CARTSLOT_EXTENSION_LIST("bin,a78")

15
src/mess/video/a7800.c
View File

@ -4,8 +4,8 @@
Routines to control the Atari 7800 video hardware
TODO:
precise DMA cycle stealing
2014-03-24 Mike Saarna Fixed DMA regarding startup, shutdown and
cycle stealing.
2013-05-08 huygens rewrite to emulate line ram buffers (mostly fixes Kung-Fu Master
Started DMA cycle stealing implementation
@ -126,7 +126,12 @@ void a7800_state::maria_draw_scanline()
int x, d, c, i, pixel_cell, cells;
int maria_cycles;
maria_cycles = 0;
//maria_cycles = 0;
if ( m_maria_offset == 0 )
maria_cycles = 5+19; // DMA startup + last line shutdown
else
maria_cycles = 5+13; // DMA startup + other line shutdown
cells = 0;
/* Process this DLL entry */
@ -198,7 +203,9 @@ void a7800_state::maria_draw_scanline()
}
}
}
m_maincpu->eat_cycles(maria_cycles/4); // Maria clock rate is 4 times that of CPU
// spin the CPU for Maria DMA, if it's not already spinning for WSYNC
if ( ! m_maria_wsync )
m_maincpu->spin_until_time(m_maincpu->cycles_to_attotime(maria_cycles/4)); // Maria clock rate is 4 times that of the CPU
// draw line buffer to screen
m_active_buffer = !m_active_buffer; // switch buffers