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Notes on data storage in VRAM 1
There are some restrictions on the storage of scroll data in the VRAM bank mentioned above due to hardware performance problems.
The details of the restrictions are not described here, but at a minimum, be sure to observe the following two conditions.
- 1) VRAM bank usage priority by scroll type
- Do not store the scroll data of the normal scroll screen and the rotary scroll screen in the same VRAM bank.
- 2) VRAM bank storage restriction for pattern name data
- All pattern name data can be stored only in a maximum of 2 banks of either VRAM_A0, B0 and VRAM_A1, B1 in the VRAM bank.
Figure 8-6 VRAM bank storage restriction for pattern name data
If these two conditions are not observed, scrolling drawing is affected as follows:
When - 1) is not observed
- The normal scroll screen data is ignored from the VRAM bank usage priority, and only the rotary scroll screen data is valid.
When
- 2) is not observed
- When the pattern name data is stored in the VRAM bank with the same number at the end of the VRAM bank name, the scroll may not be drawn correctly or not drawn at all.
PN storage restrictions
Refer to “HARDWARE MANUAL vol.2: VDP2 User's Manual” for details of PN storage limit.
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