Mercurial > repos > blastem
changeset 2012:b05295c2ad04
Small improvement to refresh cycle approximation
| author | Mike Pavone <pavone@retrodev.com> |
|---|---|
| date | Sun, 01 Nov 2020 12:35:58 -0800 |
| parents | 579fe3f6fe76 |
| children | dcdad92f84a4 |
| files | genesis.c |
| diffstat | 1 files changed, 26 insertions(+), 2 deletions(-) [+] |
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--- a/genesis.c Sun Nov 01 12:35:08 2020 -0800 +++ b/genesis.c Sun Nov 01 12:35:58 2020 -0800 @@ -583,7 +583,7 @@ vdp_test_port_write(gen->vdp, value); } #ifdef REFRESH_EMULATION - last_sync_cycle -= 4; + last_sync_cycle -= 4 * MCLKS_PER_68K; //refresh may have happened while we were waiting on the VDP, //so advance refresh_counter but don't add any delays if (vdp_port >= 4 && vdp_port < 8 && v_context->cycles != before_cycle) { @@ -674,7 +674,7 @@ value = get_open_bus_value(&gen->header); } #ifdef REFRESH_EMULATION - last_sync_cycle -= 4; + last_sync_cycle -= 4 * MCLKS_PER_68K; //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); @@ -735,6 +735,13 @@ static m68k_context * io_write(uint32_t location, m68k_context * context, uint8_t value) { genesis_context * gen = context->system; +#ifdef REFRESH_EMULATION + //do refresh check here so we can avoid adding a penalty for a refresh that happens during an IO area access + refresh_counter += context->current_cycle - 4*MCLKS_PER_68K - last_sync_cycle; + context->current_cycle += REFRESH_DELAY * MCLKS_PER_68K * (refresh_counter / (MCLKS_PER_68K * REFRESH_INTERVAL)); + refresh_counter = refresh_counter % (MCLKS_PER_68K * REFRESH_INTERVAL); + last_sync_cycle = context->current_cycle - 4*MCLKS_PER_68K; +#endif if (location < 0x10000) { //Access to Z80 memory incurs a one 68K cycle wait state context->current_cycle += MCLKS_PER_68K; @@ -859,6 +866,11 @@ } } } +#ifdef REFRESH_EMULATION + //no refresh delays during IO access + refresh_counter += context->current_cycle - last_sync_cycle; + refresh_counter = refresh_counter % (MCLKS_PER_68K * REFRESH_INTERVAL); +#endif return context; } @@ -882,6 +894,13 @@ { uint8_t value; genesis_context *gen = context->system; +#ifdef REFRESH_EMULATION + //do refresh check here so we can avoid adding a penalty for a refresh that happens during an IO area access + refresh_counter += context->current_cycle - 4*MCLKS_PER_68K - last_sync_cycle; + context->current_cycle += REFRESH_DELAY * MCLKS_PER_68K * (refresh_counter / (MCLKS_PER_68K * REFRESH_INTERVAL)); + refresh_counter = refresh_counter % (MCLKS_PER_68K * REFRESH_INTERVAL); + last_sync_cycle = context->current_cycle - 4*MCLKS_PER_68K; +#endif if (location < 0x10000) { //Access to Z80 memory incurs a one 68K cycle wait state context->current_cycle += MCLKS_PER_68K; @@ -977,6 +996,11 @@ } } } +#ifdef REFRESH_EMULATION + //no refresh delays during IO access + refresh_counter += context->current_cycle - last_sync_cycle; + refresh_counter = refresh_counter % (MCLKS_PER_68K * REFRESH_INTERVAL); +#endif return value; }