Describe the solution you'd like
This limitation should be added to the description of TEXTYPOS register (after the VIC-IV register table):
" TEXTYPOS Character generator vertical position ( must be > 0 )".
Additional context
Behavior can be reproduced in BASIC with this sequence, both on NTSC and PAL.
POKE $D02F,$47:POKE $D02F,$52:REM ENABLE VIC-IV REGISTERS
POKE $D04E,0:REM TEXT DISAPPEARS
POKE $D04E,1:REM TEXT APPEARS AGAIN (SHIFTED BELOW TOP BORDER)
Describe where we can find the problematic topic Using TEXTYPOS = 0 will cause all text to disappear, which is a known behavior, see https://discord.com/channels/719326990221574164/977076334297743360/1147845360677564466, but not documented in the Chipset Reference.
Describe the solution you'd like This limitation should be added to the description of TEXTYPOS register (after the VIC-IV register table): " TEXTYPOS Character generator vertical position ( must be > 0 )".
Additional context Behavior can be reproduced in BASIC with this sequence, both on NTSC and PAL. POKE $D02F,$47:POKE $D02F,$52:REM ENABLE VIC-IV REGISTERS POKE $D04E,0:REM TEXT DISAPPEARS POKE $D04E,1:REM TEXT APPEARS AGAIN (SHIFTED BELOW TOP BORDER)