Changes
ASIC
,*Specific ROM switching
*8-bit printer port (with bit3 of CRTC register 12)
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== Programmable Raster Interrupt ==
An 8-bit memory-mapped register (PRI) has been added within the ASIC at address 6800h, which is cleared at power up:
*When PRI=0, the classic R52 interrupt system of the [[Gate Array]] functions as before
*Otherwise, we have a raster line interrupt system instead: an interrupt will occur at the end of the scan line specified in PRI
The PRI can be reprogrammed as required to produce multiple interrupts per frame.
And there is more than that. On Amstrad Plus, we don't have a unique source of interrupts. Each DMA sound channels is also able to trigger an interrupt. And the ASIC also provides an interrupt vector register (IVR) for vectorized interrupts.
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