Changes

{| class="wikitable"|-! 6845 Selected Register !! 6845 Register data returnedData Returned|-| 0 || 16|-| 1 || 17|-| 2 || Status 1 (note 1)|-| 3 || Status 2 (note 1)|-| 4 || 12|-| 5 || 13|-| 6 || (note 2)|-| 7 || (note 2)|-| 8 || 16|-| 9 || 17|-| 10 || Status 1 (note 1)|-| 11 || Status 2 (note 1)|-| 12 || 12|-| 13 || 13|-| 14 || (note 2)|-| 15 || (note 2)|-| 16 || 16|-| 17 || 17|-| 18 || Status 1 (note 1)|-| 19 || Status 2 (note 1)|-| 20 || 12|-| 21 || 13|-| 22 || (note 2)|-| 23 || (note 2)|-| 24 || 16|-| 25 || 17|-| 26 || Status 1 (note 1)|-| 27 || Status 2 (note 1)|-| 28 || 12|-| 29 || 13|-| 30 || (note 2)|-| 31 || (note 2)|} 

* These do not appear to be actual CRTC registers. When read, they appear to give the status of the internal operation of the CRTC. I have named them "Status 1" and "Status 2" because they contain different information. These status registers are only present in the CPC+ version of the CRTC. I believe these registers were used to test the operation of the CRTC during development.* It is not clear if these registers hold any data, they always return "0".

{| class="wikitable"|-| Bit 7 || (function of this bit is unknown)|-| Bit 6 || (function of this bit is unknown)|-| Bit 5 || 0: CRTC is on last line of VSYNC|-| Bit 4 || 0: CRTC is on last char of HSYNC|-| Bit 3 || 0: CRTC Horizontal Count == Horizontal Sync Position (Reg 2)|-| Bit 2 || 0: CRTC Horizontal Count == Horizontal Displayed (Reg 1)|-| Bit 1 || 0: CRTC Horizontal Count == (Horizontal Total/2)|-| Bit 0 || 0: CRTC Horizontal Count != Horizontal Total|}

{| class="wikitable"|-| Bit 7 || 0: when RC!=0|-| Bit 6 || (function of this bit is unknown)|-| Bit 5 || 0: when RC==R9|-| Bit 4 || (function of this bit is unknown)|-| Bit 3 || (function of this bit is unknown)|-| Bit 2 || (function of this bit is unknown)|-| Bit 1 || (function of this bit is unknown)|-| Bit 0 || (function of this bit is unknown)|}