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arxiv: 2509.17355 · v1 · pith:ZF6GMBSNnew · submitted 2025-09-22 · 💻 cs.NE

CMOS Implementation of Field Programmable Spiking Neural Network for Hardware Reservoir Computing

Pith reviewed 2026-05-21 22:53 UTC · model grok-4.3

classification 💻 cs.NE
keywords spiking neural networksreservoir computingCMOS implementationneuromorphic hardwarefield programmableFORCE algorithmLIF neuronsedge computing
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The pith

A CMOS field-programmable spiking neural network implements hardware reservoir computing with low energy use.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces a CMOS-based spiking neural network architecture built for reservoir computing. It combines leaky integrate-and-fire neurons that include voltage-controlled oscillators with an on-chip FPGA to allow programmable connections and arbitrary reservoir setups. Tests show the system carries out FORCE algorithm learning along with linear and non-linear memory capacity benchmarks and NARMA10 tasks, with results matching between simulation and actual chip measurements. The design targets edge applications by keeping area small and energy low while avoiding ADCs for readout.

Core claim

The authors demonstrate a novel CMOS-implemented field-programmable neural network architecture for hardware reservoir computing. We propose a Leaky Integrate-and-Fire neuron circuit with integrated voltage-controlled oscillators and programmable weighted interconnections via an on-chip FPGA framework, enabling arbitrary reservoir configurations. The system demonstrates effective implementation of the FORCE algorithm learning, linear and non-linear memory capacity benchmarks, and NARMA10 tasks, both in simulation and actual chip measurements, achieving compact area utilization around 540 NAND2-equivalent units and low energy consumption of 21.7 pJ/pulse without requiring ADCs.

What carries the argument

Leaky Integrate-and-Fire neuron circuit with integrated voltage-controlled oscillators combined with on-chip FPGA framework for programmable weighted interconnections that enable arbitrary reservoir configurations.

If this is right

  • The architecture supports real-time learning and inference in neuromorphic systems.
  • It enables system-on-chip integration for reservoir computing applications.
  • The design provides high configurability and digital interfacing for scalable neuromorphic hardware.
  • It delivers low-power operation suitable for edge deployment of temporal processing tasks.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Local hardware processing could address privacy concerns by keeping data on-device rather than sending it to remote servers.
  • The absence of ADCs may simplify direct connection to digital control logic in mixed-signal systems.
  • The approach could extend to other time-series prediction problems common in sensor networks if the reservoir size scales with the FPGA resources.

Load-bearing premise

The on-chip FPGA framework and LIF-VCO neuron circuits can realize arbitrary reservoir configurations with sufficient stability and low enough noise to support the reported learning performance without post-fabrication tuning or external calibration.

What would settle it

Chip measurements that fail to match simulation results on the NARMA10 task or memory capacity benchmarks without external calibration or tuning would show the central claim does not hold.

Figures

Figures reproduced from arXiv: 2509.17355 by Ckristian Duran, Nanako Kimura, Tetsuya Iizuka, Zolboo Byambadorj.

Figure 1
Figure 1. Figure 1: Possible neural networks using reservoir computing. The reservoir can be configured with (a) a random linkage of neurons. This reservoir can also be configured with (b) a fixed array with neighboring connections. The values of neurons are extracted and weight-summed together to produce an output. reservoir. Different kinds of reservoirs can be configured in a neural network to obtain different kinds of com… view at source ↗
Figure 2
Figure 2. Figure 2: The neuron circuit constructed with standard CMOS technology. The leakage-integrate neuron contains the inhibition and excitation transistors, and the capacitor that integrates incoming pulses. The Voltage-Controlled Oscillators (VCOs) generate currents from the capacitor voltage Vcap, which modulates the current in ring oscillators, such as the VCOs can output different frequencies f(Vcap) (Positive VCO) … view at source ↗
Figure 3
Figure 3. Figure 3: Example of the neuron behavior. Excitations rise the capacitor voltage Vcap, while the inhibitions decrease it. The leakage occurs through time after either an inhibition or excitation happens, making the voltage tends to converge to a middle voltage between ground and supply. calculations using the integration of incoming pulses. The voltage increment and decrement can be adjusted by varying the width of … view at source ↗
Figure 4
Figure 4. Figure 4: Example of the VCO outputs inside the neuron. Excitations increase the frequency of the positive VCO and decrease that of the negative VCO. Inhibitions in contrast decrease the positive VCO frequency and increase the negative VCO frequency. When there are no incoming pulses, both VCOs oscillate at a fixed frequency related to the middle voltage between supply and ground stored in Vcap. as shown in [PITH_F… view at source ↗
Figure 5
Figure 5. Figure 5: Weighting circuit to produce the input spikes to the neuron. The input is an oscillation signal, which can come from other neurons or the input of the reservoir. The outputs are positive pulses in the case of inhibitions outinh or negative pulses for excitations outexcb. w[0:3] chooses the weight through the multiplexers by directly affecting the duration of pulses for excitation (mexc) and inhibition (min… view at source ↗
Figure 6
Figure 6. Figure 6: Block diagram of the implementation of neural networks and data extraction for optimization algorithms. The input to the reservoir is transformed into frequencies that are used for the inhibition and excitation of all neurons. The interactions between neurons and the input frequencies are configured into the chip with the different reservoir weights. The neurons are inhibited (through minh,i,j ) or excited… view at source ↗
Figure 7
Figure 7. Figure 7: Input of the reservoir conversion to inhibition and excitation frequencies. The value is filtered by positive and negative values. Each filtered value is multiplied by a constant frequency, e.g. 1 MHz. This frequency value is used for increments of a counter used as a frequency generator. The outputs of the two counters are used to generate oscillations as excitation (FEXC ) and inhibition (FINH). by a con… view at source ↗
Figure 8
Figure 8. Figure 8: Measurement of frequency and serial data read out. The state of the neuron Nk is measured by a counter. The counter increases with a frequency of 50 MHz and resets in transitions of the output of the neuron. The value of the counter is extracted using a shift register. The sample extractor uses a multi-channel serial interface to extract the value from the shift registers and stores it into registers. This… view at source ↗
Figure 9
Figure 9. Figure 9: Counter value to frequency, and then frequency to voltage conversion procedure. The dependence of the frequencies on the voltage is extracted from simulations, and adjusted using some measurement results. The frequencies are first calculated by dividing the counter clock frequency fbase by each one of the counter values. These frequencies are then used to calculate two values of the internal state of the n… view at source ↗
Figure 10
Figure 10. Figure 10: The FORCE algorithm. The output is always fed back to the neural network. FORCE compares the output with a teaching waveform during a period of time named the teaching period. The error between the teaching and the output is used in the RLS procedure, which modifies the output weights dynamically. Once the teaching period is over, the system just keeps feeding back the output prediction to the input of th… view at source ↗
Figure 11
Figure 11. Figure 11: Datapath architecture of the RLS filter and linear accelerator. The datapath contains 50 multipliers, an unsigned divider, storage of the output weights, and storage for temporal calculations used by the RLS filter. takes the values from the VCO measurements and convert them to the approximate state of the neuron Vcap as xˆ(n). The datapath contains 50 multipliers and an adder which perform their calculat… view at source ↗
Figure 12
Figure 12. Figure 12: The open loop algorithm. The reservoir accepts a time-independent series of random inputs from −1 to 1 and records the state of the neurons at the output. Depending of the evaluation benchmark, the procedure takes several delays of the input signal and perform calculations to set the teaching signal z(n). The weighted sum of the neuron state is the prediction of the teaching signal zp(n). The procedure se… view at source ↗
Figure 13
Figure 13. Figure 13: Architecture of the reservoir and chip micrograph. The left is a breakdown of the architecture of the configurable reservoir, and the right is the micrograph of the chip, along with the layout of a single neuron. The reservoir is composed of 100 neurons, with additional hardware to support configurable routing and weighting. The chip spans an area of 2 × 2 mm2 containing all hardware for connecting the re… view at source ↗
Figure 14
Figure 14. Figure 14: Measurement setup of the proposed reservoir. The board above (blue) includes the FPGA that contains the processing and accelerators such as the RISC￾V system, the Counter-Voltage Conversion (CVC), the RLS accelerator, and the frequency generators for the neural network inputs FINH and FEXC . This FPGA communicates with the reservoir board (green) that is mounted below. This reservoir board interfaces the … view at source ↗
Figure 15
Figure 15. Figure 15: FORCE algorithm measurement and simulation results. The test involves feeding a sine wave with different frequencies. The learning takes place during 15 cycles of the teaching signal, and the test takes place in the next 5 cycles. The measurement of the correlation is done in the testing time. This figure shows an example of the FORCE learning with the input frequency of 220 Hz. This example shows a compa… view at source ↗
Figure 16
Figure 16. Figure 16: Memory capacity measurements on the hardware reservoir. Examples of the memory capacity learning at delays k = 1, 3 with measurements (left) and simulations (right) are shown for comparison. The circuit was supplied with a total of 200 inputs using normal distribution between [−1, 1]. The output of all neurons is sampled with ts = 120 µs. The first 10% of the sample are ignored, the next 70% of the sample… view at source ↗
Figure 17
Figure 17. Figure 17: Non-linear memory capacity benchmarks on the hardware reservoir. This figure also shows examples of the non-linear memory capacity learning at delays k = 1, 3 with measurements (left) and simulations (right) for comparison. The circuit was supplied with a total of 3000 inputs using normal distribution between [−1, 1]. The output of all neurons is sampled with ts = 120 µs. The first 10% of the sample are i… view at source ↗
Figure 18
Figure 18. Figure 18: NARMA10 test result using (a) the physical reservoir measurements and (b) its simulation. The blue waveform indicates the teaching period, and the black waveform indicates test period. During the teaching, the captured data of the neurons are used to optimize the weights of the output. The test only uses those final weights over the rest of the test. Regardless of teaching or testing periods, the predicti… view at source ↗
Figure 12
Figure 12. Figure 12: The optimization ignores the initial 10% of the samples because samples [PITH_FULL_IMAGE:figures/full_fig_p030_12.png] view at source ↗
read the original abstract

The increasing complexity and energy demands of large-scale neural networks, such as Deep Neural Networks (DNNs) and Large Language Models (LLMs), challenge their practical deployment in edge applications due to high power consumption, area requirements, and privacy concerns. Spiking Neural Networks (SNNs), particularly in analog implementations, offer a promising low-power alternative but suffer from noise sensitivity and connectivity limitations. This work presents a novel CMOS-implemented field-programmable neural network architecture for hardware reservoir computing. We propose a Leaky Integrate-and-Fire (LIF) neuron circuit with integrated voltage-controlled oscillators (VCOs) and programmable weighted interconnections via an on-chip FPGA framework, enabling arbitrary reservoir configurations. The system demonstrates effective implementation of the FORCE algorithm learning, linear and non-linear memory capacity benchmarks, and NARMA10 tasks, both in simulation and actual chip measurements. The neuron design achieves compact area utilization (around 540 NAND2-equivalent units) and low energy consumption (21.7 pJ/pulse) without requiring ADCs for information readout, making it ideal for system-on-chip integration of reservoir computing. This architecture paves the way for scalable, energy-efficient neuromorphic systems capable of performing real-time learning and inference with high configurability and digital interfacing.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript presents a CMOS implementation of a field-programmable spiking neural network for hardware reservoir computing. It uses LIF neurons integrated with VCOs for readout and an on-chip FPGA framework for programmable weighted interconnections to enable arbitrary reservoir configurations. The work reports successful demonstration of the FORCE learning algorithm, linear and non-linear memory capacity benchmarks, and NARMA10 tasks in both simulation and actual chip measurements, while emphasizing compact area utilization (540 NAND2-equivalent units) and low energy consumption (21.7 pJ/pulse) without requiring ADCs, positioning the design as suitable for system-on-chip neuromorphic integration.

Significance. If the on-chip measurements prove robust and reproducible, this architecture could meaningfully advance energy-efficient, configurable reservoir computing hardware for edge applications. The compact LIF-VCO design and FPGA-based programmability address key limitations in analog SNN implementations, offering a pathway to scalable, low-power real-time learning systems that mitigate the power and area demands of conventional DNNs.

major comments (2)
  1. [Abstract] Abstract: The central claim of effective chip measurements for FORCE learning, linear/non-linear memory capacity, and NARMA10 tasks is not supported by error bars, dataset sizes, or quantitative comparisons to simulation results; without these the evidence for hardware performance remains limited and potentially affected by unstated selection or calibration effects.
  2. [Circuit and Architecture Description] Neuron and system description: The LIF-VCO circuits and FPGA framework are presented as realizing arbitrary reservoir configurations with sufficient stability, yet no quantification of threshold mismatch, VCO jitter, or reservoir-state stability under CMOS process variation is provided; this is load-bearing for the claim that the design supports the reported learning performance without post-fabrication tuning or external calibration.
minor comments (2)
  1. [Abstract] The abstract and results sections would benefit from explicit statements of the CMOS process node and supply voltage used for the reported area and energy figures.
  2. [Results] Figure captions for measurement results should include the number of trials or runs averaged to allow assessment of variability.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments and the positive assessment of the work's potential. We address each major comment below and outline the revisions we will make to strengthen the presentation of the hardware results and circuit analysis.

read point-by-point responses
  1. Referee: [Abstract] Abstract: The central claim of effective chip measurements for FORCE learning, linear/non-linear memory capacity, and NARMA10 tasks is not supported by error bars, dataset sizes, or quantitative comparisons to simulation results; without these the evidence for hardware performance remains limited and potentially affected by unstated selection or calibration effects.

    Authors: We agree that the abstract would benefit from clearer indication of the supporting quantitative evidence. The main text already reports results from multiple experimental runs on the fabricated chip with standard deviations shown in the relevant figures and tables for the FORCE learning, memory capacity, and NARMA10 tasks. In the revised manuscript we will update the abstract to reference these details explicitly (including dataset sizes of 2000 samples per task and direct side-by-side simulation-versus-hardware metrics). All presented hardware data come from complete measurement sets without post-selection or external calibration beyond the on-chip FPGA configuration. revision: yes

  2. Referee: [Circuit and Architecture Description] Neuron and system description: The LIF-VCO circuits and FPGA framework are presented as realizing arbitrary reservoir configurations with sufficient stability, yet no quantification of threshold mismatch, VCO jitter, or reservoir-state stability under CMOS process variation is provided; this is load-bearing for the claim that the design supports the reported learning performance without post-fabrication tuning or external calibration.

    Authors: We concur that explicit quantification of device-level variations would reinforce the robustness claims. The architecture uses the on-chip FPGA to realize arbitrary weighted connections digitally, which inherently compensates for analog mismatches without external tuning. In the revision we will add a short subsection reporting measured VCO jitter and observed neuron-to-neuron threshold spread from the fabricated chip, together with evidence that reservoir-state stability is maintained across the demonstrated tasks. A comprehensive Monte-Carlo process-variation study, however, was not performed in the original work. revision: partial

Circularity Check

0 steps flagged

No circularity: hardware implementation and measurement report

full rationale

This is an implementation-focused paper describing a CMOS LIF-VCO neuron circuit, FPGA-programmable interconnections, and measured performance on FORCE learning, memory capacity, and NARMA10 tasks in both simulation and silicon. No derivation chain, first-principles equations, or predictions are presented that reduce claimed results to fitted parameters or self-citations by construction. Performance claims rest on direct circuit measurements and task benchmarks rather than any self-referential mathematical reduction, satisfying the self-contained criterion with no load-bearing circular steps.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on standard assumptions of CMOS circuit behavior and measurement fidelity; no new physical entities or fitted constants are introduced in the abstract.

axioms (1)
  • domain assumption Standard CMOS process parameters and analog circuit models hold without unexpected parasitic effects dominating the LIF and VCO dynamics.
    Implicit in any claim of functional on-chip spiking behavior.

pith-pipeline@v0.9.0 · 5770 in / 1281 out tokens · 39557 ms · 2026-05-21T22:53:34.704938+00:00 · methodology

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