tepples wrote:
7. Writing to video memory during draw time, at a rate of a few bytes per line.
8 bytes per active part of a line and 11 bytes during HBL (but you're not gonna be able to hit all of the access slots due to different and denser grouping making it impossible for Z80 to hit all those slots). 10 or 11 bytes will be doable without any headache.
Code:
Ideal case access figures for Z80 using OUTI instruction :
+---------+-----------------------+-----------------------+
| | 50Hz | 60Hz |
| +-------+-------+-------+-------+-------+-------+
| | V192 | V224 | V240 | V192 | V224 | V240 |
+---------+-------+-------+-------+-------+-------+-------+
| Active | 2123 | 2475 | 2651 | 2123 | 2475 | 2640 |
| Passive | 1710 | 1254 | 1026 | 983 | 527 | 0 |
| A + P | 3833 | 3729 | 3677 | 3106 | 3002 | 2640 |
| Blanked | 4460 | 4460 | 4460 | 3733 | 3733 | 3420 |
+---------+-------+-------+-------+-------+-------+-------+
Number of tiles that can be transferred per frame :
+---------+--------------------+--------------------+
| | 50Hz | 60Hz |
| +------+------+------+------+------+------+
| | V192 | V224 | V240 | V192 | V224 | V240 |
+---------+------+------+------+------+------+------+
| Active | 66 | 77 | 82 | 66 | 77 | 82 |
| Passive | 53 | 39 | 32 | 30 | 16 | 0 |
| A + P | 119 | 116 | 114 | 97 | 93 | 82 |
| Blanked | 139 | 139 | 139 | 116 | 116 | 106 |
+---------+------+------+------+------+------+------+
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