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Fix regression in Konami games from address/cd latch changes
author Mike Pavone <pavone@retrodev.com>
date Fri, 17 Apr 2020 22:20:08 -0700
parents abc89555f2e0
children c3c62dbf1ceb
comparison
equal deleted inserted replaced
1928:abc89555f2e0 1929:c7e3e3ebb64a
3693 3693
3694 static void clear_pending(vdp_context *context) 3694 static void clear_pending(vdp_context *context)
3695 { 3695 {
3696 context->flags &= ~FLAG_PENDING; 3696 context->flags &= ~FLAG_PENDING;
3697 context->address = context->address_latch; 3697 context->address = context->address_latch;
3698 context->cd = context->cd_latch; 3698 //It seems like the DMA enable bit doesn't so much enable DMA so much
3699 //as it enables changing CD5 from control port writes
3700 if (context->regs[REG_MODE_2] & BIT_DMA_ENABLE) {
3701 context->cd = context->cd_latch;
3702 } else {
3703 context->cd = (context->cd & 0x20) | (context->cd_latch & 0x1F);
3704 }
3699 } 3705 }
3700 3706
3701 int vdp_control_port_write(vdp_context * context, uint16_t value) 3707 int vdp_control_port_write(vdp_context * context, uint16_t value)
3702 { 3708 {
3703 //printf("control port write: %X at %d\n", value, context->cycles); 3709 //printf("control port write: %X at %d\n", value, context->cycles);
3704 if (context->flags & FLAG_DMA_RUN) { 3710 if (context->flags & FLAG_DMA_RUN) {
3705 return -1; 3711 return -1;
3706 } 3712 }
3707 if (context->flags & FLAG_PENDING) { 3713 if (context->flags & FLAG_PENDING) {
3708 context->address_latch = (context->address_latch & 0x3FFF) | (value << 14 & 0x1C000); 3714 context->address_latch = (context->address_latch & 0x3FFF) | (value << 14 & 0x1C000);
3709 //It seems like the DMA enable bit doesn't so much enable DMA so much 3715 context->cd_latch = (context->cd_latch & 0x3) | ((value >> 2) & ~0x3 & 0xFF);
3710 //as it enables changing CD5 from control port writes
3711 uint8_t preserve = (context->regs[REG_MODE_2] & BIT_DMA_ENABLE) ? 0x3 : 0x23;
3712 context->cd_latch = (context->cd_latch & preserve) | ((value >> 2) & ~preserve & 0xFF);
3713 clear_pending(context); 3716 clear_pending(context);
3714 //Should these be taken care of here or after the first write? 3717 //Should these be taken care of here or after the first write?
3715 context->flags &= ~FLAG_READ_FETCHED; 3718 context->flags &= ~FLAG_READ_FETCHED;
3716 context->flags2 &= ~FLAG2_READ_PENDING; 3719 context->flags2 &= ~FLAG2_READ_PENDING;
3717 //printf("New Address: %X, New CD: %X\n", context->address, context->cd); 3720 //printf("New Address: %X, New CD: %X\n", context->address, context->cd);