diff options
Diffstat (limited to 'vdp.c')
| -rw-r--r-- | vdp.c | 31 |
1 files changed, 23 insertions, 8 deletions
@@ -487,7 +487,7 @@ void external_slot(vdp_context * context) } case VSRAM_WRITE: if (((start->address/2) & 63) < VSRAM_SIZE) { - //printf("VSRAM Write: %X to %X\n", start->value, context->address); + //printf("VSRAM Write: %X to %X @ vcounter: %d, hslot: %d, cycle: %d\n", start->value, context->address, context->vcounter, context->hslot, context->cycles); context->vsram[(start->address/2) & 63] = start->partial == 2 ? context->fifo[context->fifo_write].value : start->value; } @@ -659,9 +659,24 @@ void read_map_scroll(uint16_t column, uint16_t vsram_off, uint32_t line, uint16_ vscroll <<= 1; vscroll |= 1; } - //TODO: Further research on vscroll latch behavior and the "first column bug" seen in Gynoug - //this should be close, but won't match the exact behavior Eke-Eke has written about - if (column == 2 || (column && (context->regs[REG_MODE_3] & BIT_VSCROLL))) { + //TODO: Further research on vscroll latch behavior and the "first column bug" + if (!column) { + if (context->regs[REG_MODE_3] & BIT_VSCROLL) { + if (context->regs[REG_MODE_4] & BIT_H40) { + //Based on observed behavior documented by Eke-Eke, I'm guessing the VDP + //ends up fetching the last value on the VSRAM bus in the H40 case + //getting the last latched value should be close enough for now + if (!vsram_off) { + context->vscroll_latch[0] = context->vscroll_latch[1]; + } + } else { + //supposedly it's always forced to 0 in the H32 case + context->vscroll_latch[0] = context->vscroll_latch[1] = 0; + } + } else { + context->vscroll_latch[vsram_off] = context->vsram[vsram_off]; + } + } else if (context->regs[REG_MODE_3] & BIT_VSCROLL) { context->vscroll_latch[vsram_off] = context->vsram[column - 2 + vsram_off]; } vscroll &= context->vscroll_latch[vsram_off] + line; @@ -1664,9 +1679,9 @@ int vdp_control_port_write(vdp_context * context, uint16_t value) if (reg == REG_BG_COLOR) { value &= 0x3F; } - if (reg == REG_MODE_4 && ((value ^ context->regs[reg]) & BIT_H40)) { + /*if (reg == REG_MODE_4 && ((value ^ context->regs[reg]) & BIT_H40)) { printf("Mode changed from H%d to H%d @ %d, frame: %d\n", context->regs[reg] & BIT_H40 ? 40 : 32, value & BIT_H40 ? 40 : 32, context->cycles, context->frame); - } + }*/ context->regs[reg] = value; if (reg == REG_MODE_4) { context->double_res = (value & (BIT_INTERLACE | BIT_DOUBLE_RES)) == (BIT_INTERLACE | BIT_DOUBLE_RES); @@ -1952,9 +1967,9 @@ uint32_t vdp_cycles_to_line(vdp_context * context, uint32_t target) } } else { if (context->vcounter < jump_start) { - lines = jump_start - context->vcounter + 512 - jump_dst + 1; + lines = jump_start - context->vcounter + 512 - jump_dst; } else { - lines = 512 - context->vcounter + 1; + lines = 512 - context->vcounter; } if (target < jump_start) { lines += target; |