On CPC, HSYNC and VSYNC from the CRTC are passed into the Gate-Array.
When HSYNC is active Gate-Array and ASIC output outputs the palette colour black. If the HSYNC is set to 14 characters then black will be output for 14us.
The HSYNC is modified before being sent to the monitor. It happens 2us after the HSYNC from the CRTC and lasts 4us when HSYNC length is greater or equal to 6.
If R2=46, and HSYNC width is 14 then monitor hsync starts at 48 and lasts until 51. On a CPC monitor, the HSYNC is rendered in "absolute black". It is darker than the black output by the Gate-Array/ASIC. (The colours of the CPC are subject to black level, contrast and brightness, the SYNC black is not).
== The 6845 Registers ==