diff --git a/src/mame/drivers/cit101.cpp b/src/mame/drivers/cit101.cpp
index 160c538eab3..9069265c1ea 100644
--- a/src/mame/drivers/cit101.cpp
+++ b/src/mame/drivers/cit101.cpp
@@ -174,6 +174,10 @@ void cit101_state::draw_line(uint32_t *pixptr, int minx, int maxx, int line, boo
 
 u32 cit101_state::screen_update(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect)
 {
+	// While screen height is fixed at 240 pixels, the number of character rows and the height of each row are not.
+	// The "Set-Up" screens configure 3 ordinary 10-pixel rows on the top (using two for double-height characters)
+	// and 2 more on the bottom, separated by 11 blank rows of 16 pixels and 1 blank row of 14 pixels.
+
 	const u8 scrattr = m_extraram[0];
 
 	int y = 0;