Video Generation Circuitry; Color Computer 2 Address Decoding - Radio Shack TRS-80 Service Manual

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SLENB*
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74LS02
R/W
-----11-. . . .
E
MEMRD*
-
ROMA*
E
ROMB*
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CTS*
PIAO*
S2
c
PIA1*
S1
B
SCS*
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A
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U22
U11
SAM
74LS138
Figure 4-7. Color Computer 2 Address Decoding
Additional details of the
SAM
chip may be obtained by
referring to the MC6883 data sheet.
4.4 Video Generation Circuitry (U8)
A computer without some method of providing output to the
user would not be of much value. In the Color Computer 2,
the main method of providing output is via the RF modulator
CU9) which provides a composite chroma signal into a
standard color (or black and white) television on channel 3
or 4. However, most of the modulator's job is to translate
computer-like signals into signals the television can use.
The portion of the Color Computer
2
that actually generates
the computer-like video signals is U8, the MC6847 Video
Display Generator, or VDG chip.
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