== Memory Mapped I/O Ports ==
{|{{Prettytable|width: 700px; font-size: 2em;}}class="wikitable"|'''!Mem'''||'''!Decoded as'''||'''!Port'''||'''!Read'''||'''!Write'''
|-
|#4000-7FFF||%01xxxxxx xxxxxxxx||ASIC - CPC+/GX4000 registers|| Read || Write
The [[ASIC]] I/O page is defined as follows:
{|{{Prettytable|width: 700px; font-size: 2em;}}class="wikitable"! ADDR !! SIZE !! POR !! TYPE !! MNEM !! USE
|-
| 4000h || 100h || N || R/W || || Sprite 0 image data
POR column indicates whether a register has power on reset. A "N" indicates that the contents of a register are undefined at power on.
A colour in the palette is coded in 2 bytes:
* For first byte, bit7..4 is blue value, bit3..0 is red value
* For second byte, bit7..4 is ignored, bit3..0 is green value
Sprite magnification is coded in 1 byte:
* bit7..3 is ignored
* bit3..2 is X magnification (00 = not displayed, 01 = x1, 10 = x2, 11 = x4)
* bit1..0 is Y magnification (00 = not displayed, 01 = x1, 10 = x2, 11 = x4)
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