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) |
|