Changes
CRTC
,/* Status register on Type 1 */
The UM6845R has a status register that can be read using port &BExx.
Bit 6 is set to 1 if there is a strobe input to the /LPEN signal. It is cleared to 0 when either R17 or R16 (LPEN address) of the CRTC are read. It signals there is a valid LPEN input. On my CPC (arnoldemuKevin Thacker) with UM6845R, it is triggered at power on, R17 and R16 have the values 0 when read.
Bit 5 is set to 1 when CRTC is in "vertical blanking". Vertical blanking is when the vertical border is active. i.e. VCC>=R6.
