On CPC, the HSYNC and VSYNC signals are received from the [[CRTC]]. These signals are then modified and merged by the Gate Array into a single CSYNC signal that will be sent to the display.
When HSYNC is active Gate-Array 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.
The VSYNC is also modified before being sent to the monitor. It happens two lines* after the VSYNC from the CRTC and stay two lines (same cut rule if VSYNC is lower than 4). PAL (50Hz) does need two lines VSYNC_width, and 4us HSYNC_width.
The Gate Array uses 2 internal counters to create its CSYNC signal: