Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1992-03-31
1992-10-20
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358153, H04N 504
Patent
active
051574926
ABSTRACT:
A tuning system includes a microcomputer-based synchronization signal detector which does not require the use of a hardware timer/counter. The microcomputer samples the output signal of a sync separator coupled to an ordinary input/output port during a number of different evaluation intervals to determine if respective characteristics of a valid sync signal occur. During one evaluation interval, a test is performed to determine if a "high" level is present for a time duration less than a given time duration (e.g. 10 .mu.S) corresponding to the maximum duration of horizontal sync pulses. During another evaluation interval, a test is performed to determine if a "low" level is present for a time duration greater than another given time duration (e.g., 40 .mu.S) corresponding to the minimum separation between horizontal sync pulses. The sampling intervals and evaluation intervals are established by the time required to execute instruction cycles.
REFERENCES:
patent: 4464679 (1984-08-01), Wargo
patent: 4654708 (1987-03-01), de la Guardia et al.
patent: 4729023 (1988-03-01), Srivastava et al.
Emanuel Peter M.
Groody James J.
Harvey D.
Shedd Robert D.
Thomson Consumer Electronics Inc.
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