DEC VT220 Technical Manual 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