AMI Decoder apparatus
AssigneeInternational Telephone and Telegraph Corporation
InventorVictor M. Hernandez
Life of this patent
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Abstract
A decoder is provided which does not require the use of a retiming circuit. The decoder operates with an AMI signal, and operates to detect a transition occurring at the center of a bit cell to blank out those transitions which do not coincide with the encoding clock. The decision is made by examining the time between received transitions. Once this is accomplished, an asynchronous logic circuit with two states of memory can be used to structure the decoded AMI data into a NRZ or other format by storing the transitions which occur in the middle of the previous bit cell and outputting a first binary value during the following bit cell for a transition, or if no transitions have occurred in the middle of the previous bit cell, a second binary value is outputted during the following bit period.
Claims11
A decoder apparatus for use in a data transmission system in which information is conveyed in a bit stream consisting of a plurality of sequential bit cells, said stream of the type employing an alternate mark inversion (AMI) code, wherein the start of each bit cell is manifested by a first transition, each bit cell having a given duration T, with those bits indicative of a first binary value further possessing a transition at the center of said bit duration (T/2) to distinguish this first binary value from a second binary bit value with those bits of said second value having no transition at said center, said decoder comprising:
- transition detector means responsive to said AMI bit stream for providing at an output, a plurality of pulses indicative of each transition in said AMI bit stream, whereby said plurality of pulses has at least a separate pulse for the start of each bit and a pulse indicative of a transition at the center of those bits of said first value,
- center bit cell detector means responsive to said plurality of pulses at the output of said transition detector for responding to only those pulses indicative of said center transition, and therefore of said first binary value,
- logic means responsive to said plurality of pulses from said transition detector means and said detected pulses to provide at an output, a digital signal indicative of the information conveyed by said AMI code, by outputting a first binary level during a next succeeding start pulse when a transition was detected at the center of a previous pulse, and outputting a second binary level when a transition was not detected, whereby said output digital signal manifests the original information encoded within said AMI bit stream.
Dependencies are inferred from the claim text.