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VBLANK

VBLANK = $01

Control the vertical blank signal.

Ground port path.

Latch control.

WRITE
Name
D7
D6
D5
D4
D3
D2
D1
D0
$01
VBLANK
DUMP
LATCH
X
X
X
X
VBLANK
X

Details

Control vertical blank and the latches and dumping transistors on the input ports.

FunctionValues
DUMP
D7
Dump path to ground for I6, I1, I2, and I3 ports0 = Remove dump path
1 = Dump I6, I1, I2, and I3 ports to ground
LATCH
D6
I4, I5 Latch Control0 = Disable I4 and I5 latches, reset latches to logic TRUE
1 = Enable I4 and I5 latches
VBLANK
D1
Vertical Blank0 = Stop Vertical Blank
1 = Start Vertical Blank

TV Frame

A typical TV frame will consists of 3 vertical sync VSYNC lines, 37 vertical blank (VBLANK) lines, TV picture lines (NTSC=192, PAL=242), and 30 overscan lines. See My First Kernel for a code example of the simplest use of VSYNC and VBLANK to form a correct TV frame.

see TIA
see VSYNC
see My First Kernel