Parallel decimation circuits
View Patent ↗A decimation system and decimation circuit for decimating waveform data on an oscilloscope. The decimation circuit is implemented using sixteen parallel 16-to-1 multiplexers connected in parallel to a data bus which selectively captures samples based on control signals generated by a sample counting circuit. Decimation factor and phase values can be input to program the amount of decimation performed by the circuit. The decimation system provides even more flexibility in controlling the decimation and is formed by combining several of the decimation circuits with corresponding analog-to-digital converters and memory segments.
1. A decimation circuit for decimating waveform data on a data acquisition system, comprising:
a sample counting circuit having N registers connected in series with one of N−1 adders positioned between each register pair, where N is the number of data lines on a data bus; the sample counting circuit determining N outputs on the basis of a decimation factor value and a decimation phase value, each output indicating a position of a data sample within the waveform data to remain after decimation; the first of the registers being set to the decimation phase value as its indicated position, each adder adding the decimation factor value to the output of the preceding register to produce the output for the next register as its indicated position; and
a multiplexing circuit having N parallel multiplexers, each being connected in series to one of N corresponding parallel output registers; each multiplexer having N parallel inputs connected with the data lines of said data bus and being controlled in accordance with a predetermined one of the outputs from said sample counting circuit to select data samples from one of the data lines of the data bus as indicated by said predetermined one of the outputs; each of said N output registers being enabled by an enable bit to receive data samples selected by the corresponding multiplexer.
2. The decimation circuit according to claim 1 , further comprising N modulus circuits and N divide circuits, each being connected to one of said N outputs from said sample counting circuit, each corresponding to a predetermined one of the N parallel multiplexers and output registers; each modulus circuit generating a clock signal for controlling the selection of data samples by the corresponding multiplexer; each divide circuit generating a locale signal for use in generating said enable bit for the corresponding output register.
3. The decimation circuit according to claim 2 , further comprising an enable circuit having at least one counter connected to N parallel comparators; each comparator comparing a count value from the counter with the locale signal received from a corresponding one of the divide circuits to generate said enable bit for the corresponding output register.
4. The decimation circuit according to claim 3 , wherein said count value sequences up to said decimation factor value then re-sequences.
5. A decimation system for decimating waveform data on a data acquisition system, comprising:
a plurality of analog-to-digital converters for acquiring and generating data samples in parallel from an input waveform;
a plurality of decimation circuits connected in parallel, each decimation circuit being connected to a predetermined corresponding one of said analog-to-digital converters and having:
a sample counting circuit having N registers connected in series with one of N−1 adders positioned between each register pair, where N is the number of data lines on a data bus; the sample counting circuit determining N outputs on the basis of a decimation factor value and a decimation phase value, each output indicating a position of a data sample within the waveform data to remain after decimation; the first of the registers being set to the decimation phase value as its indicated position, each adder adding the decimation factor value to the output of the preceding register to produce the output for the next register as its indicated position; and
a multiplexing circuit having N parallel multiplexers, each being connected in series to one of N corresponding parallel output registers; each multiplexer having N parallel inputs connected with the data lines of said data bus and being controlled in accordance with a predetermined one of the outputs from said sample counting circuit to select data samples from one of the data lines of the data bus as indicated by said predetermined one of the outputs; each of said N output registers being enabled by an enable bit to receive data samples selected by the corresponding multiplexer;
a plurality of memory segments, each memory segment for storing data samples from a predetermined corresponding one of said plurality of decimation circuits; and
a processor for selecting data samples stored in said plurality of memory segments, thereby generating the decimated waveform data.
6. The decimation system according to claim 5 , wherein said plurality of parallel analog-to-digital converters sample said waveform data at predetermined sequential times to generate waveform data samples.
7. The decimation system according to claim 5 , wherein said plurality of decimation circuits further comprises N modulus circuits and N divide circuits connected to said N outputs from said sample counting circuit and corresponding to the N parallel multiplexers and output registers; each modulus circuit generating a clock signal for controlling the selection of data samples by the corresponding multiplexer; each divide circuit generating a locale signal for use in generating said enable bit for the corresponding output register.
8. The decimation system according to claim 7 , wherein said plurality of decimation circuits further comprises an enable circuit having at least one counter connected to N parallel comparators; each comparator comparing a count value from the counter with the locale signal from one of the divide circuits to generate said enable bit for the corresponding output register.
9. The decimation system according to claim 8 , wherein said count value sequences up to said decimation factor value then re-sequences.
10. A method of decimating waveform data on a data acquisition system using a decimation circuit, comprising the steps of:
determining N outputs on the basis of a decimation factor value and a decimation phase value, each output indicating a position of a data sample within the waveform data to remain after decimation; said N outputs being determined in parallel using N registers connected in series with one of N−1 adders positioned between each register pair, where N is the number of data lines on a data bus; setting the first of the registers to the decimation phase value as its indicated position and adding the decimation factor value to the output of the preceding register using each adder to produce the output for the next register as its indicated position; and
selecting data samples of the waveform data as indicated by said N outputs from one of the data lines of said data bus; the data samples being selected using N parallel multiplexers, each being connected in series to one of N corresponding parallel output registers; each multiplexer having N parallel inputs connected with the data lines of said data bus and being controlled in accordance with a predetermined one of the N outputs from said determining step; enabling each of the N output registers using an enable bit to receive the data samples selected by the corresponding multiplexer.
11. The method according to claim 10 , further comprising the step of generating N clock signals on the basis of said N outputs from said determining step for controlling the selection of data samples by the N parallel multiplexers, and generating N locale signals on the basis of the N outputs for use in generating the enable bits for the N output registers.
12. The method according to claim 10 , further comprising the step of comparing a count value from a counter with each of the N locale signals to generate the enable bits for the N output registers.
13. The method according to claim 12 , wherein said comparing step sequences said count value up to said decimation factor value then re-sequences the count value.
14. A decimation circuit for decimating waveform data on a data acquisition system, comprising:
a sample counting circuit having N registers connected in series with one of N−1 adders positioned between each register pair, where N is the number of data lines on a data bus; the sample counting circuit determining N outputs on the basis of a decimation factor value and a decimation phase value, each output indicating a position of a data sample within the waveform data to remain after decimation; one or more of the registers being set to the decimation phase value as its indicated position, each adder adding the decimation factor value to the output of the preceding register to produce the output for one or more of the next registers as its indicated position; and
a multiplexing circuit having N parallel multiplexers, each being connected in series to one of N corresponding parallel output registers; each multiplexer having N parallel inputs connected with the data lines of said data bus and being controlled in accordance with a predetermined one of the outputs from said sample counting circuit to select data samples from one of the data lines of the data bus as indicated by said predetermined one of the outputs; each of said N output registers being enabled by an enable bit to receive data samples selected by the corresponding multiplexer.
15. The decimation circuit according to claim 14 , wherein a plurality of the registers sample data from the same position within the waveform.
16. The decimation circuit according to claim 15 , wherein the plurality of registers sampling data from the same position each store a portion of the sampled data to corresponding memory locations.
17. The decimation circuit according to claim 16 , wherein stored data is substantially evenly distributed across all memory.
18. The decimation circuit according to claim 14 , wherein the data acquisition system is part of an oscilloscope.
19. A decimation system for decimating waveform data on a data acquisition system, comprising:
a plurality of analog-to-digital converters for acquiring and generating data samples in parallel from an input waveform;
a plurality of decimation circuits connected in parallel, each decimation circuit being connected to a predetermined corresponding one of said analog-to-digital converters and having:
a sample counting circuit having N registers connected in series with one of N−1 adders positioned between each register pair, where N is the number of data lines on a data bus; the sample counting circuit determining N outputs on the basis of a decimation factor value and a decimation phase value, each output indicating a position of a data sample within the waveform data to remain after decimation; at least two of the registers being set to the decimation phase value as its indicated position, each adder adding the decimation factor value to the output of the preceding register to produce the output for at least two of the next registers as their indicated position; and
a multiplexing circuit having N parallel multiplexers, each being connected in series to one of N corresponding parallel output registers; each multiplexer having N parallel inputs connected with the data lines of said data bus and being controlled in accordance with a predetermined one of the outputs from said sample counting circuit to select data samples from one of the data lines of the data bus as indicated by said predetermined one of the outputs; each of said N output registers being enabled by an enable bit to receive data samples selected by the corresponding multiplexer;
a plurality of memory segments, each memory segment for storing data samples from a predetermined corresponding one of said plurality of decimation circuits, at least two of said one or more registers storing redundant data to their corresponding memory segments; and
a processor for selecting data samples stored in said plurality of memory segments, thereby generating the decimated waveform data.
20. A method of decimating waveform data by a data acquisition system using a decimation circuit, comprising the steps of:
determining N outputs on the basis of a decimation factor value and a decimation phase value, each output indicating a position of a data sample within the waveform data to remain after decimation; said N outputs being determined in parallel using N registers connected in series with one of N−1 adders positioned between each register pair, where N is the number of data lines on a data bus; setting the first one or more of the registers to the decimation phase value as its indicated position and adding the decimation factor value to the output of the preceding register using each adder to produce the output for the next one or more registers as their indicated position; and
selecting data samples of the waveform data as indicated by said N outputs from one of the data lines of said data bus; the data samples being selected using N parallel multiplexers, each being connected in series to one of N corresponding parallel output registers; each multiplexer having N parallel inputs connected with the data lines of said data bus and being controlled in accordance with a predetermined one of the N outputs from said determining step; and
enabling each of the N output registers using an enable bit to receive the data samples selected by the corresponding multiplexer.
21. The method according to claim 20 , wherein a plurality of the registers sample data from the same position within the waveform.
22. The method according to claim 21 , wherein the plurality of registers sampling data from the same position each store a portion of the sampled data to corresponding memory locations.
23. The method according to claim 20 , wherein stored data is substantially evenly distributed across all memory.
24. The method according to claim 20 , wherein the data acquisition system is part of an oscilloscope.