Sprites will be displayed at coordinates based on the internal counters of the CRTC. Sprite X coordinate is based on HCC. Sprite Y coordinate is based on VCC and VLC.
When the data for a sprite is read or written, that sprite is removed from the display for the duration of the access. Thus sprite data should only be accessed during retraced time or while the raster is scanning somewhere else, otherwise there is a risk of disruption of the display. [[Original Arnold V Specs|Source]]
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The Amstrad Plus ASIC improved a lot of the old CPC's capability.
Yet this was a bit flawed.
*Despite removing some tasks from the CPU ([[Z80]]), ASIC registers are mapped onto memory from #4000 to #7FFF range prior to other type of memory (RAM or ROM). That means this memory range is not accessible when ASIC registers are paged.
*PPI emulation is not correct as the original 8255 does not need validation. On ASIC emulation, this validation is needed so some programs written for "old CPCs" will not be able to get keyboard state.
*Reducing horizontal blanking could cause another internal conflict when using DMA lists. In the worst case, this conflict can cause irreversible damage to the ASIC.
*Original CPC colors emulation is not correctcolours are slightly different.
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POR column indicates whether a register has power-on reset. A "N" indicates that the contents of a register are undefined at power-on.
Writes to unused areas of the ASIC I/O page are not persisted. [https://www.cpcwiki.eu/forum/games/harrier-attack-reloaded/msg247703/#msg247703 Source]
Beware, when booting your software from cartridge. Z80 is in Interrupt Mode 0 by default. Stack Pointer is uninitialized. FDC is in DMA mode by default. And hardware sprites memory has random value.
Anyway, you have to initialize all internal components (Z80, PPI, CRTC, AY, etc) when you are booting from cartridge.
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==Related pages==
*[[Arnold V specs]]*[[Original Arnold V Specs Revised]]
*[[Extra CPC Plus Hardware Information]]
*[https://www.cpcwiki.eu/index.php/Amstrad_Cartridge_Identification_Device ACID] Protection chip used in the cartridges of the Plus series and the GX4000 game console
*[[Programming:Unlocking ASIC]]
*[[B-ASIC]]