The MOS 6567/6569 video controller (VIC-II)
and its application in the Commodore 64
Contents
3. Description of the VIC
3.7. Text/bitmap display
3.7.3. Graphics modes
3.7.3.9. Idle state
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In idle state, the VIC reads the graphics data from address $3fff (resp. $39ff if the ECM bit is set) and displays it in the selected graphics mode, but with the video matrix data (normally read in the c-accesses) being all "0" bits. So the byte at address $3fff/$39ff is output repeatedly.

c-access

No c-accesses occur.

Data
11 10 9 8 7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 0 0 0 0 0

g-access

Adresses (ECM=0)
13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 1 1 1 1 1 1 1 1 1 1 1 1 1

Adresses (ECM=1)
13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 1 1 0 0 1 1 1 1 1 1 1 1 1

Data
7 6 5 4 3 2 1 0
Standard text mode
Multicolor text mode
ECM text mode
8 pixels (1 bit/pixel)

"0": Background color 0 ($d021)
"1": Black
Standard bitmap mode
Invalid text mode
Invalid bitmap mode 1
8 pixels (1 bit/pixel)

"0": Black (background)
"1": Black (foreground)
Multicolor bitmap mode
4 pixels (2 bits/pixel)

"00": Background color 0 ($d021)
"01": Black (background)
"10": Black (foreground)
"11": Black (foreground)
Invalid bitmap mode 2
4 pixels (2 bits/pixel)

"00": Black (background)
"01": Black (background)
"10": Black (foreground)
"11": Black (foreground)