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Theory of Operation
3–18
1780R-Series Service Manual
Table 3–2: Input Channel Selection Logic
per i M e
p
(U1415) (U1415)
Par
Mode
Internal
Reference
O
per
at
i
ng
M
od
e
In
p
ut(s)
I
1
I
2
I
3
I
4
I
5
I
6
I
7
I
8
SINGLE INPUT A 0 0 0 0 0 0 0 0 CH A
SINGLE INPUT B1 0 0 0 1 0 0 0 0 CH B1
SINGLE INPUT B2 0 0 1 0 0 0 0 0 CH B2
SINGLE INPUT B3 0 0 1 1 0 0 0 0 CH B3
SINGLE INPUT PROBE 0 1 1 1 0 0 0 0 PROBE
DIFFERENTIAL A B1 0 0 0 0 1 0 0 0 CH A
DIFFERENTIAL B1 B2 0 0 0 1 1 0 1 0 CH B1
DIFFERENTIAL B1 B3 0 0 0 1 1 1 0 0 CH B1
PARADE A + B1 1 0 0 0 0 0 0 1 CH A
PARADE A + PROBE 1 0 0 1 0 0 0 1 CH A
PARADE B1 + PROBE 1 0 1 0 0 0 0 1 CH B1
PARADE B1 + B2 + B3 1 1 1 1 0 0 0 1 CH B1
PARADE B1 B2 + B2 B3 0 0 0 1 1 1 1 1 CH B1
OVERLAY A + B1 1 0 0 0 0 0 0 0 CH A
OVERLAY A + PROBE 1 0 0 1 0 0 0 0 CH A
OVERLAY B1 + PROBE 1 0 1 0 0 0 0 0 CH B1
OVERLAY B1 + B2 + B3 1 1 1 1 0 0 0 0 CH B1
OVERLAY B1 + B2 1 1 0 0 0 0 0 0 CH B1
OVERLAY B1 + B3 1 1 0 1 0 0 0 0 CH B1
OVERLAY B2 + B3 1 1 1 0 0 0 0 0 CH B1
WFM + CAL A + CAL 0 0 0 0 0 0 1 0 CH A
WFM + CAL B1 + CAL 0 0 0 1 0 0 1 0 CH B1
WFM + CAL B2 + CAL 0 0 1 0 0 0 1 0 CH B2
WFM + CAL B3 + CAL 0 0 1 1 0 0 1 0 CH B3
WFM + CAL PROBE + CAL 0 1 1 1 0 0 1 0 PROBE
CALIBRATOR CAL SIG 0 1 0 1 0 0 1 0 GROUND
CALIBRATOR OSC CAL OSC 0 1 0 1 0 1 0 0 GROUND
Decoders U1316 and U1523 convert the 3-bit logic array outputs to single active
high signals. When an input mode requires dynamic switching of inputs, such as
A/B Parade or B1-B2/B1-B3, the U1415 state machines cycle their outputs
through the appropriate sequence, timed by sync and the horizontal retrace pulse.