diff options
| -rw-r--r-- | genesis.c | 6 | ||||
| -rw-r--r-- | vdp.c | 5 |
2 files changed, 4 insertions, 7 deletions
@@ -296,12 +296,6 @@ static m68k_context * vdp_port_write(uint32_t vdp_port, m68k_context * context, sync_components(context, 0); gen->bus_busy = 0; } - if (!(v_context->flags & FLAG_DMA_RUN)) { - //two more slots of delay are needed to kill sufficient sprite capacity in Overdrive - //TODO: Measure exact value with logic analyzer - vdp_run_context(v_context, v_context->cycles + 1); - vdp_run_context(v_context, v_context->cycles + 1); - } } if (blocked < 0) { @@ -2482,13 +2482,16 @@ int vdp_control_port_write(vdp_context * context, uint16_t value) // if((context->regs[REG_DMASRC_H] & 0xC0) != 0x80) { //DMA copy or 68K -> VDP, transfer starts immediately - context->flags |= FLAG_DMA_RUN; context->dma_cd = context->cd; //printf("DMA start (length: %X) at cycle %d, frame: %d, vcounter: %d, hslot: %d\n", (context->regs[REG_DMALEN_H] << 8) | context->regs[REG_DMALEN_L], context->cycles, context->frame, context->vcounter, context->hslot); if (!(context->regs[REG_DMASRC_H] & 0x80)) { //printf("DMA Address: %X, New CD: %X, Source: %X, Length: %X\n", context->address, context->cd, (context->regs[REG_DMASRC_H] << 17) | (context->regs[REG_DMASRC_M] << 9) | (context->regs[REG_DMASRC_L] << 1), context->regs[REG_DMALEN_H] << 8 | context->regs[REG_DMALEN_L]); + //68K -> VDP DMA takes 4 slots to actually start reading even though it acquires the bus immediately + vdp_run_context(context, context->cycles + 16 * ((context->regs[REG_MODE_2] & BIT_MODE_5) && (context->regs[REG_MODE_4] & BIT_H40) ? 4 : 5)); + context->flags |= FLAG_DMA_RUN; return 1; } else { + context->flags |= FLAG_DMA_RUN; //printf("DMA Copy Address: %X, New CD: %X, Source: %X\n", context->address, context->cd, (context->regs[REG_DMASRC_M] << 8) | context->regs[REG_DMASRC_L]); } } else { |