Commodore 1940 - Page 30

4.3 Mode Switching Circuit
<Fig.8 Video Output Circuit>
Vertical size and linearity of VGA mode are determined by the horizontal and vertical sync polarity using exclusive
or gate IC (IC601 74LS86). The polarity of each IC
601 pin is as follow:
PIN
NO:
,,"<
"
'*. ",
1
2
'3
4
5
6
1.;8
~ ..
10
.. 11
12
13
SYNC HIGH
H
H L H H H H H H L
H
H
LOW L L L L H L L H L L
L
L
27