diff options
| -rw-r--r-- | genesis.c | 10 |
1 files changed, 7 insertions, 3 deletions
@@ -283,9 +283,9 @@ static m68k_context * vdp_port_write(uint32_t vdp_port, m68k_context * context, sync_components(context, 0); genesis_context * gen = context->system; vdp_context *v_context = gen->vdp; + uint32_t before_cycle = v_context->cycles; if (vdp_port < 0x10) { int blocked; - uint32_t before_cycle = v_context->cycles; if (vdp_port < 4) { while (vdp_data_port_write(v_context, value) < 0) { while(v_context->flags & FLAG_DMA_RUN) { @@ -361,8 +361,12 @@ static m68k_context * vdp_port_write(uint32_t vdp_port, m68k_context * context, last_sync_cycle -= 4; //refresh may have happened while we were waiting on the VDP, //so advance refresh_counter but don't add any delays - refresh_counter += (context->current_cycle - last_sync_cycle); - refresh_counter = refresh_counter % (MCLKS_PER_68K * REFRESH_INTERVAL); + if (vdp_port >= 4 && vdp_port < 8 && v_context->cycles != before_cycle) { + refresh_counter = 0; + } else { + refresh_counter += (context->current_cycle - last_sync_cycle); + refresh_counter = refresh_counter % (MCLKS_PER_68K * REFRESH_INTERVAL); + } last_sync_cycle = context->current_cycle; #endif return context; |