LUM0-LUM3: Digital luminance signal to TV modulator (?)
CSYNC: (unknown)
HALT: (usage unknown)
Vss: Ground (?)
OSC: Output to console speaker (?)
F0O: (unknown)
Ø2: Clock in (?)
CS: Chip select
R/W: Read/write direction
Note: I have no confirmation of the above descriptions. This is just
my best educated guess, using my knowledge of microcomputer design, the
function of the C/GTIA processor, and the interaction between the custom
IC's.