== Split screen ==
The 8-bit register SPLT register (at address 6801h) specifies the scan line where the screen split occurs. Setting this register to 0 (the default value at power-up) disables the split screen feature.
The 16-bit register SSA register (high byte at address 6802h and low byte at address 6803h) defines the starting address in memory for displaying the lower part of the screen. SSA works similarly to the duo R12/R13 in the CRTC. This configuration allows the lower part of the screen to be sourced from a different memory area and be scrolled independently. However, note that the soft scrolling register SSCR acts on the whole screen.
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