DEC VT220 - Page 126

Table 6-3
Video Logic Schematic References
Circuit/ Board
Schematic
Component
Ref. No.' s
Page Loc.
ACCESS MUX
E30
4 B3
ADDRESS BUFFER
E8
4 D6
ADDRESS MUX E25
4
D4
ALT CHAR GEN RAM
E12,E22,E24,R74
4
D4/C3/B3
ATR/CHAR GATE
E46,R62
3
B4
ATTRIBUTE RAM
E5,E6 1 C3-C2
ATTRIBUTE LATCH
1
E21,E38
4
B7
ATTRIBUTE
LATCH
2
E29 4 B6
ATTRIBUTE
LATCH
3
E28,E38
4
B4
ATTRIBUTE
LATCH
4
E50,E46
5 D7/D6
BLANK CIRCUITS E22,E39,E44,E50
5 C8-C5
CHAR GEN ROM E13,R73
4
C3
CHAR LATCH 1 E19,E22,E39
4 C7/A4
CHAR LATCH 2
E20
4
C4
CLR GATE
E22
4
A4
COMPOSITE VIDEO E49,C55,C56,L3,Q1,
5 D3-D1
OUTPUT STAGE
R4,R12-R17
CRT 9007 VPAC E16,E24,R57,R58 2 B2-C2
CRT CLK GATE E34,R75,R6 3
B3
CURSOR SKEW F/F E32,E38 5
B8
DATA GATE
E46 5
D4
DOT CLOCK GENERATOR
E24,E34,R60,Y3,Y4
3
B6-B4
INH F/F E35,E37
5
A6/A7
INH GATE
E37
5
B7
INH LATCH
E50 5
C6
INPUT
STAGE E45,E49
5
D4-C4
JI
J1
5 CI-Al
J3 J3
5
Cl
LBF WR GATES E42
3
D6
LINE BUF ADDRESS COUNTER
E7
4
D7-C7
LINE BUFFER RAM E14
4
D5
LOAD F/F E35,E41
5
B7/B6
piS CONVERTER
E27
5
B5
READ/WRITE BUFFER
E18
4
D2
SERIAL LATCH
E36,E45
5
B4-B3
SIN LATCH
E36,E41
5
B5/B4
SYNC BUFFERS
E44,E48,R9,R10
5
B3
SYNC DMA LATCH
E29
4
B6
T1
GATES
E42
3
C6
T5 H
LATCH
E43
3
C4
T5 L
LATCH
E36,E44
5
B4
UL ATR GATES
E37,E44,E45
5
C8-C7
VIDEO OUTPUT
STAGE
Q2,R18-R20,R23-R25
5
C3-C2
6-42