Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Patent
1997-11-17
2000-12-19
Pham, Chi H.
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
375370, 375354, 370520, H03K 2100
Patent
active
061635502
ABSTRACT:
A state dependent synchronization circuit synchronizes an asynchronous input signal to a clock signal to generate a synchronous output signal. The circuit synchronizes both the leading edge and the trailing edge of the input signal and also maintains the state of the output signal at a level corresponding to the input signal when the input signal does not change. The circuit includes an input signal latch which receives the input signal and provides a latched signal which does not charge state even if the input signal subsequently changes state until the latched signal is synchronized to the clock signal. The circuit further includes a synchronizer which synchronizes the latched signal with the clock signal. The synchronizer provides feedback signals to the input signal latch to permit the input signal latch to recognize a change in the state of the input signal only after the synchronizer has synchronized the previous state of the input signal. The synchronizer preferably includes a first stage and a second stage. The first stage of the synchronizer isolates the second stage from any oscillation which may occur if the latched signal changes state too close to a transition in the clock signal. The first stage and the second stage of the synchronizer preferably operate on opposite edges of the clock signal. The circuit preferably includes a pair of cross-coupled gates that enable the circuit to recognize and synchrinize pulses of very short duration.
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Alston Jerald
Chan Ting-Li
Duong Frank
Pham Chi H.
QLogic Corporation
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