Circuit and method for high speed bit stream capture using a digital delay line
First Claim
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1. A high-speed bit stream capture circuit, comprising:
- a transmission interface unit for receiving an incoming bit stream and producing therefrom a high-speed bit stream;
a digital delay line coupled to said transmission interface unit, including a plurality of digital delay elements coupled in series and a plurality of taps, each tap coupled to the output of a distinct digital delay element of said plurality of digital delay elements, for receiving and delaying the high-speed bit stream;
a latch having a plurality of latch inputs, each latch input being coupled to a respective tap of said plurality of taps, and a latch control input for receiving a latch control signal for latching and outputting through a plurality of latch outputs parallel data at said plurality of latch inputs; and
a counter for counting to a prescribed number of bit stream periods from the start of said bit stream and, when said prescribed number of bit stream periods is counted, generating said latch control signal.
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Abstract
A digital delay line, comprising adjustable digital delay elements, receives and buffers an incoming bit stream by repeatedly delaying bits of the bit stream for a specific period of time. The outputs of selected adjustable digital delay elements are tapped for inspecting in parallel a specific pattern of bits of the bit stream. A programmable counter counts bit periods and generates a latch control signal to latch those specific bits at any offset within the bit stream before the entirety of the bit stream is received.
39 Citations
18 Claims
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1. A high-speed bit stream capture circuit, comprising:
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a transmission interface unit for receiving an incoming bit stream and producing therefrom a high-speed bit stream;
a digital delay line coupled to said transmission interface unit, including a plurality of digital delay elements coupled in series and a plurality of taps, each tap coupled to the output of a distinct digital delay element of said plurality of digital delay elements, for receiving and delaying the high-speed bit stream;
a latch having a plurality of latch inputs, each latch input being coupled to a respective tap of said plurality of taps, and a latch control input for receiving a latch control signal for latching and outputting through a plurality of latch outputs parallel data at said plurality of latch inputs; and
a counter for counting to a prescribed number of bit stream periods from the start of said bit stream and, when said prescribed number of bit stream periods is counted, generating said latch control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
said digital delay line further includes a calibration input for receiving a calibration signal; and
each of said plurality of digital delay elements comprises a calibration input for receiving said calibration signal and in response adjusts the delay period thereof.
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3. The high-speed bit stream capture circuit of claim 2, wherein each digital delay element comprises:
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a first adjustable inverter, having a first calibration input for receiving said calibration signal; and
a second adjustable inverter, having a second calibration input for receiving said calibration signal, coupled in series to said first switchable inverter.
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4. The high-speed bit stream capture circuit of claim 1, wherein the delay period of each of said plurality of digital delay elements is the same.
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5. The high-speed bit stream capture circuit of claim 1, wherein the delay period of each of said plurality of digital delay elements is at least 140 ps.
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6. The high-speed bit capture circuit of claim 1, wherein each of said plurality latch inputs is coupled to a respective tap of said plurality of taps.
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7. The high-speed bit capture circuit of claim 1, wherein said counter is configured for modifying said prescribed number according to a signal indicative of a new prescribed number of bit stream periods.
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8. The high-speed bit capture circuit of claim 1, wherein the prescribed number is less than the total number of bit stream periods in said bit stream.
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9. The high-speed bit capture circuit of claim 1, wherein said transmission interface unit includes a buffer for receiving a single ended bit stream and producing therefrom said high-speed bit stream applied to said digital delay line.
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10. The high-speed bit capture circuit of claim 9, wherein said transmission interface unit includes a level shifter for shifting the voltage level of said single ended bit stream.
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11. The high-speed bit capture circuit of claim 1, wherein said transmission interface unit includes a comparator for comparing a differentially encoded bit stream and producing therefrom said high-speed bit stream applied to said digital delay line.
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12. A method of capturing bits from a high-speed bit stream, comprising the steps of:
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receiving the high-speed bit stream;
repeatedly delaying by a delay period a plurality of bits from said high-speed bit stream;
tapping said plurality of bits in parallel to produce parallel data;
counting bit stream periods of said high-speed bit stream; and
latching said parallel data when a prescribed number of bit stream periods is counted. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification