To specify the onboard RAM size of the emulated CDP18S020 Evaluation Kit (between 256 bytes and 4 Kb) use the 'RAM' spin button (yellow ellipse).
4 dip switches (orange ellipse) are available on the CDP18S020 front panel, switch these up (see dip switch 2 below) to enable RAM memory protection (disable writing to RAM).
Each dip switch controls 1 KB of RAM at hex address: