Mercurial > repos > simple16
changeset 4:8170d60f188b
Added basic rendering timing outline and made some other minor spec changes
| author | Michael Pavone <pavone@retrodev.com> |
|---|---|
| date | Fri, 25 Mar 2016 19:26:23 -0700 |
| parents | 08b69e3f9f17 |
| children | 18b66690ae13 |
| files | simple_console.txt |
| diffstat | 1 files changed, 16 insertions(+), 2 deletions(-) [+] |
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--- a/simple_console.txt Fri Mar 25 09:06:29 2016 -0700 +++ b/simple_console.txt Fri Mar 25 19:26:23 2016 -0700 @@ -126,7 +126,7 @@ F = fine scroll bit x = unused E: Write Dest Address : Read Status -F: Write Data : Read Data +F: Write Data : Read ??? Name Table Start Address: @@ -149,8 +149,10 @@ Only values of 7E and 7F are valid for these bits at present 8 LSB determine offset (1 LSB ignored) -Writing to Data port puts word into FIFO +Writing to Data port puts value into a one word FIFO Offset within memory type is increment when word is pulled from FIFO +Writing to the FIFO when it is full will cause the existing entry to be overwritten + Pattern Format: 4bpp in an 8x8 tile arrangement @@ -195,3 +197,15 @@ H-Counter goes from 0-415 and then wraps back to zero V-Counter goes from 0-261 and then wraps back to zero V-Counter increments when H-Counter wraps + +Rendering Process: +208 main VRAM access slots +123 slots for background +160-123 = 37 extra slots during active display + 48 slots during inactive display +80 slots for sprite rendering +5 slots remain for refresh or external access + +Since sprite rendering needs to intrude on active display period, +a double buffered line buffer is needed. Useful for VGA compatibility anyway +