Mercurial > repos > blastem
diff vdp.c @ 149:139e5dcd6aa3
Make writes to control and data port block when DMA is in progress
| author | Mike Pavone <pavone@retrodev.com> |
|---|---|
| date | Tue, 01 Jan 2013 07:06:57 -0800 |
| parents | e5487ef04619 |
| children | 6b593ea0ed90 |
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--- a/vdp.c Tue Jan 01 07:04:48 2013 -0800 +++ b/vdp.c Tue Jan 01 07:06:57 2013 -0800 @@ -184,7 +184,7 @@ //TODO: Figure out what happens if CD bit 4 is not set in DMA copy mode //TODO: Figure out what happens when CD:0-3 is not set to a write mode in DMA operations //TODO: Figure out what happens if DMA gets disabled part way through a DMA fill or DMA copy - if((context->regs[REG_MODE_2] & BIT_DMA_ENABLE) && (context->flags & FLAG_DMA_RUN)) { + if(context->flags & FLAG_DMA_RUN) { uint16_t dma_len; switch(context->regs[REG_DMASRC_H] & 0xC0) { @@ -1022,6 +1022,9 @@ int vdp_control_port_write(vdp_context * context, uint16_t value) { //printf("control port write: %X\n", value); + if (context->flags & FLAG_DMA_RUN) { + return -1; + } if (context->flags & FLAG_PENDING) { context->address = (context->address & 0x3FFF) | (value << 14); context->cd = (context->cd & 0x3) | ((value >> 2) & 0x3C); @@ -1057,9 +1060,16 @@ return 0; } -void vdp_data_port_write(vdp_context * context, uint16_t value) +int vdp_data_port_write(vdp_context * context, uint16_t value) { //printf("data port write: %X\n", value); + if (context->flags & FLAG_DMA_RUN) { + return -1; + } + if (!(context->cd & 1)) { + //ignore writes when cd is configured for read + return 0; + } context->flags &= ~FLAG_PENDING; /*if (context->fifo_cur == context->fifo_end) { printf("FIFO full, waiting for space before next write at cycle %X\n", context->cycles); @@ -1074,6 +1084,7 @@ context->fifo_cur->partial = 0; context->fifo_cur++; context->address += context->regs[REG_AUTOINC]; + return 0; } uint16_t vdp_control_port_read(vdp_context * context) @@ -1086,7 +1097,7 @@ if (context->fifo_cur == context->fifo_end) { value |= 0x100; } - if ((context->regs[REG_MODE_2] & BIT_DMA_ENABLE) && (context->flags & FLAG_DMA_RUN)) { + if (context->flags & FLAG_DMA_RUN) { value |= 0x2; } uint32_t line= context->cycles / MCLKS_LINE;