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| programmable_bitmap_sequencer [2020/09/28 17:27] – [Principles of operation] laubzega | programmable_bitmap_sequencer [2022/07/14 15:20] – [Principles of operation] silverdr |
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| The first condition is normally met, so no point worrying about it. \\ | The first condition is normally met, so no point worrying about it. \\ |
| As soon as ''S_ACTIVE'' is set, VASYL starts paying attention to the contents of ''S_CYC_START'' and ''S_CYC_STOP'' registers. Normally, after power up or reset these registers are set respectively to 15 and 55, values that correspond to the left and right edges of visible display area. In other words, by default, if ''S_ACTIVE'' is set, PBS overrides all forty memory accesses in any given display line. This is convenient, but by no means required - our window can be as narrow a single cycle. For example, to approximate the configuration visible in the picture, we could set ''S_CYC_START'' to 15+5=20 and ''S_CYC_STOP'' to 55-12=43. | As soon as ''S_ACTIVE'' is set, VASYL starts paying attention to the contents of ''S_CYC_START'' and ''S_CYC_STOP'' registers. Normally, after power up or reset these registers are set respectively to 15 and 55, values that correspond to the left and right edges of visible display area. In other words, by default, if ''S_ACTIVE'' is set, PBS overrides all forty memory accesses in any given display line. This is convenient, but by no means required - our window can be as narrow as a single cycle. For example, to approximate the configuration visible in the picture, we could set ''S_CYC_START'' to 15+5=20 and ''S_CYC_STOP'' to 55-12=43. |
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| Once PBS decides to act, it performs following operations in every cycle: | Once PBS decides to act, it performs following operations in every cycle: |
