Sensor circuit, pixel circuit, and method for controlling a pixel circuit

Abstract

A sensor circuit and a pixel circuit that can reduce a response time of an event sensor and reduce false detection are provided. A sensor circuit has a connection point between a source terminal of a MOS transistor and a light-receiving element, and has an amplifier having an input connected to the connection point for outputting a voltage depending on a logarithm of a photoelectric current of the light-receiving element, wherein an output of the amplifier is connected to a gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage depending on the logarithm of the photoelectric current. The sensor circuit further includes a capacitance for a negative capacitance generator (NCG).

Description

Technical Field

[0001] This invention relates to sensor circuits, pixel circuits, and methods for controlling pixel circuits, and more specifically, to sensor circuits having logarithmic conversion outputs, pixel circuits used as event sensors, and methods for controlling pixel circuits. Background Technology

[0002] Event-based sensors, also known as dynamic vision sensors (DVS), have attracted attention as a novel type of imaging device for mobile terminals. Event-based sensors capture the brightness changes of each pixel as "events" and output their information, offering advantages such as low latency, low power consumption, and high dynamic range. This detection capability is required in feature point extraction for simultaneous localization and mapping (SLAM) technology applied to autonomous robots. Furthermore, this detection capability is essential for detecting high-speed images of fast-moving objects, reconstructing high-resolution images, compensating for motion blur, and frame interpolation. However, since the response latency of event sensors depends on brightness, the temporal accuracy of event detection decreases as brightness decreases. Summary of the Invention

[0003] The purpose of this invention is to provide a sensor circuit and pixel circuit that can reduce the response time of an event sensor and reduce false detections of the event sensor.

[0004] A first embodiment of the present invention provides a sensor circuit having a connection point between the source terminal of a MOS transistor and a photoreceiving element, and a first inverting amplifier having an input terminal connected to the connection point for outputting a voltage dependent on the logarithm of the photocurrent of the photoreceiving element. The output terminal of the first inverting amplifier is connected to the gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage dependent on the logarithm of the photocurrent. The sensor circuit further includes a second inverting amplifier having an input terminal connected to the output terminal of the first inverting amplifier, and an output terminal connected to the connection point via a capacitor.

[0005] According to the first embodiment, a negative capacitor can be formed using an existing inverting amplifier, while suppressing the expansion of the circuit size.

[0006] A second embodiment of the present invention provides a sensor circuit having a connection point between the source terminal of a MOS transistor and a photoreceiving element, and an amplifier having an input terminal connected to the connection point for outputting a voltage that depends on the logarithm of the photocurrent of the photoreceiving element. The output terminal of the amplifier is connected to the gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage that depends on the logarithm of the photocurrent. The amplifier is a differential amplifier having an inverting input terminal connected to the connection point, a non-inverting output terminal connected to the gate terminal, and an inverting output terminal connected to the connection point via a capacitor.

[0007] According to the second embodiment, it is not necessary to add the second inverting amplifier in the first embodiment.

[0008] A third embodiment of the present invention provides a pixel circuit comprising: a sensor circuit having a connection point between a source terminal of a MOS transistor and a photoreceiving element; a first inverting amplifier having an input terminal connected to the connection point, the connection point being used to output a voltage dependent on the logarithm of the photocurrent of the photoreceiving element; wherein the output terminal of the first inverting amplifier is connected to the gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage dependent on the logarithm of the photocurrent; and a second inverting amplifier connected to the output terminal of the sensor circuit and used as a sample-and-hold circuit to hold the input voltage and amplify the change in the output terminal of the sensor circuit. The pixel circuit further includes a capacitor inserted between the output terminal of the second inverting amplifier and the connection point.

[0009] According to the third embodiment, the negative capacitance generation (NCG) circuit can be configured without adding a non-inverting amplifier.

[0010] In the third embodiment, a buffer amplifier can be inserted before the second inverting amplifier. The buffer amplifier can, for example, adjust the signal bandwidth and operating point.

[0011] A fourth embodiment of the present invention provides a method for controlling a pixel circuit, the method comprising: a sensor circuit having a connection point between a source terminal of a MOS transistor and a photoreceiving element, and a first inverting amplifier having an input terminal connected to the connection point, the connection point being used to output a voltage, the voltage depending on the logarithm of the photocurrent of the photoreceiving element, wherein the output terminal of the first inverting amplifier is connected to the gate terminal of the MOS transistor, and the gate terminal is adjusted to a certain voltage, the voltage depending on the logarithm of the photocurrent; and a second inverting amplifier connected to the output terminal of the sensor circuit and used as a sample-and-hold circuit to hold the input voltage and amplify the change in the output terminal of the sensor circuit, the method being executed by an initial program circuit of the pixel circuit, comprising the following steps: if the difference between the output of the sensor circuit and the held value of the sample-and-hold circuit exceeds a given threshold voltage, sensing a reset signal for resetting the held value of the sample-and-hold circuit and sending an event signal to an arbitrator circuit; and releasing the reset signal upon completion of communication with the arbitrator circuit.

[0012] According to the fourth embodiment, the recoil voltage during reset is small, so the input of photocurrent is not affected. Attached Figure Description

[0013] [ Figure 1A ] Figure 1A This is a schematic diagram of a traditional sensor circuit with logarithmic conversion output;

[0014] [ Figure 1B ] Figure 1B This is a schematic diagram of a traditional sensor circuit with logarithmic conversion output;

[0015] [ Figure 2 ] Figure 2 This is a schematic diagram of the pixel circuit provided in the first embodiment of the present invention;

[0016] [ Figure 3A ] Figure 3A This is a schematic diagram of the operation sequence of a traditional pixel circuit;

[0017] [ Figure 3B ] Figure 3B This is a schematic diagram of the operation sequence of the pixel circuit in the first embodiment;

[0018] [ Figure 4 ] Figure 4 This is a pattern diagram of the pixel circuit provided in the second embodiment of the present invention;

[0019] [ Figure 5 ] Figure 5This is a schematic diagram of the modification of the pixel circuit provided in the second embodiment;

[0020] [ Figure 6A ] Figure 6A This is a schematic diagram of the inverting amplifier of the pixel circuit provided in the second embodiment;

[0021] [ Figure 6B ] Figure 6B This is a schematic diagram of the differential amplifier of the pixel circuit provided in the second embodiment;

[0022] [ Figure 7 ] Figure 7 This is a schematic diagram of the pixel circuit provided in the third embodiment of the present invention;

[0023] [ Figure 8A ] Figure 8A This is a schematic diagram of the capacitor structure of the negative capacitance generating circuit provided in the fourth embodiment of the present invention;

[0024] [ Figure 8B ] Figure 8B This is a schematic diagram of another capacitor structure in the negative capacitance generation circuit provided in the fourth embodiment;

[0025] [ Figure 9 ] Figure 9 This is a schematic diagram of the variable capacitor structure of the negative capacitor generation circuit provided in the fourth embodiment. Detailed Implementation

[0026] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] Figure 1A A conventional sensor circuit with a logarithmic conversion output is shown. The source terminal of the MOS transistor Tr is connected to the cathode terminal of a photodiode (PD), which is a light-receiving element. The connection point is the logarithmic conversion output LOG-OUT, which provides the output that depends on the logarithm of the photocurrent. When the MOS transistor Tr operates in the subthreshold region, the gate-source voltage V... gs It is logarithmically proportional to the photocurrent, as shown below.

[0028] [Equation 1]

[0029]

[0030] Among them, I ph It is the drain current corresponding to the photocurrent, I0 is the saturation current, and V th is the threshold voltage, kT / q is the thermal voltage, and n is a constant determined by the structure of the MOS transistor. Therefore, as... Figure 1AAs shown, when the gate voltage is constant, the voltage at the junction becomes a voltage that depends on the logarithm of the photocurrent, and the photocurrent is converted into the logarithmic output LOG-OUT.

[0031] like Figure 1A As shown, since the photodiode (PD) and MOS transistor Tr are configured as source followers biased by the photocurrent flowing through the photodiode (PD), the response time of the sensor circuit is dominated by the settling time of the source follower and depends on the photocurrent. Here, the settling time of the source follower is determined by the parasitic capacitance (C) between the gate and source of the MOS transistor Tr. g ) and the parasitic capacitance (C) of the photodiode (PD) as the load. P Therefore, when the illuminance is low, the response time is worse because the photodiode (PD) has a smaller photocurrent.

[0032] Therefore, as Figure 1B As shown, it is known that a method for reducing the effective load capacitance (C) using a photodiode (PD) is employed. P The feedback control amplifier 11 is an inverting amplifier that receives the logarithmic conversion output as the photocurrent input and applies feedback control to the gate terminal of the MOS transistor Tr. When the gain of amplifier 11 is –A, the voltage amplitude of the photodiode (PD) is suppressed to 1 / (1+A), thus suppressing the effective load capacitance to 1 / (1+A).

[0033] It is also known that a negative capacitance generator (NCG) is used as a method to reduce the effective load capacitance (see, for example, Patent Document 1). The NCG is a non-inverting amplifier that uses capacitor C... pF Apply positive feedback. When the amplifier gain is A, the input capacitance C... NEG Equation 2 shows that when the gain A > 1, the input capacitor becomes a negative capacitor.

[0034] [Equation 2]

[0035] C NEG =C p (1-A) (2)

[0036] Similar to the active matrix sensor in Patent Document 1, the effective load capacitance can be reduced by connecting the NCG to the logarithmic conversion output (photocurrent input) of the pixel circuit. This method can shorten the settling time of the source follower.

[0037] However, the former type of feedback control has limitations in reducing the effective load capacitance for the following reasons: First, when the feedback amplifier is configured as a common-source amplifier, the gain is limited to approximately 50 times. Second, the parasitic capacitance (C) at the gate terminal of the MOS transistor Tr... g Third, the slew rate of the source follower limits the voltage change in the photodiode (PD). Therefore, there are limitations to shortening the response time of the event sensor.

[0038] Furthermore, when the latter type of NCG is applied to the pixel circuit shown in Figure 1, the implementation of a non-inverting amplifier results in increased power consumption and larger circuit size in the pixel circuit.

[0039] Therefore, in this embodiment, a new NCG is implemented in the pixel circuit.

[0040] First Embodiment

[0041] Figure 2 A pixel circuit according to a first embodiment of the present invention is shown. The source terminal of a MOS transistor Tr is connected to the cathode terminal of a photodiode (PD), which is a light-receiving element. The connection point serves as a logarithmic conversion output LOG-OUT, which provides an output dependent on the logarithm of the photocurrent of the light-receiving element. An amplifier 21 with an input connected to the connection point outputs a voltage (V). log This voltage depends on the logarithm of the photocurrent, which varies based on the intensity of the incident light incident on the photodiode (PD). Furthermore, the output of amplifier 21 is connected to the gate terminal of the MOS transistor Tr, and the gate terminal is regulated to a voltage that depends on the logarithm of the photocurrent.

[0042] An inverting amplifier, including capacitors C1 and C2 and amplifier 22, is connected to the output of the sensor circuit. A switch SW, short-circuiting the input and output, is connected to amplifier 22 and acts as a sample-and-hold circuit with capacitor C1 to sample the output of the sensor circuit. One sampling period begins when switch SW is open. Since the output of the sensor circuit at the aforementioned time is the reference level, amplifier 22 amplifies and outputs the change in the sensor circuit output. That is, the input at the time switch SW is open is the reference level, and the inverting amplifier amplifies the voltage change of the logarithmic converter output into a voltage (V) representing the brightness change. diff ).

[0043] The output of the inverting amplifier is connected to detectors 23 and 24. Once the output terminal voltage (V) diffIf the voltage exceeds a given threshold, detector 23 outputs an event detection signal (ON). event The output terminal voltage is the difference between the output of the sensor circuit and the value held by the sample-and-hold circuit. Similarly, once the output terminal voltage (V...) diff If the voltage is lower than a given threshold voltage, detector 24 outputs an event detection signal (OFF). event Therefore, detectors 23 and 24 can detect positive and negative brightness changes, respectively. Once the initial program circuit 25 detects that the output of the sample-and-hold circuit exceeds a given threshold, the initial program circuit 25 controls the switch SW to reset the reference value used for detecting brightness changes. Furthermore, when an event detection signal is received, the initial program circuit 25 outputs an event signal for post-processing by the peripheral circuitry.

[0044] In the pixel circuit of this embodiment, the capacitor C used for feedback F It is also inserted between the output terminal of amplifier 22 and the cathode terminal of the photodiode (PD). That is, between the input and output terminals of the two cascaded amplifiers 21 and 22, in other words, through capacitor C... F Positive feedback is applied between the photocurrent input of amplifier 21 and the brightness change output of amplifier 22. This configuration corresponds to connecting the NCG to the logarithmic conversion output (photocurrent input) of the pixel circuit. Wherein, when the gain of amplifier 21 is A1, the input capacitance C of the photocurrent input... NEG It is represented by Formula 3.

[0045] [Equation 3]

[0046]

[0047] Therefore, the NCG can be configured without adding a non-inverting amplifier. The negative capacitance of the NCG can be reduced in the effective load capacitance. That is, the parasitic capacitance (C) of the gate terminal of the MOS transistor Tr is reduced. g The effective load capacitance in a photodiode (PD) can be obtained through... Figure 1B The feedback control shown decreases as the effective load capacitance decreases. Therefore, the response time of the event sensor can be further reduced.

[0048] Figure 3A The operating sequence of a conventional pixel circuit is shown. For comparison, the conventional sequence executed by the initial program circuit 25 is shown. Once the output terminal voltage (V) is output as a brightness change, diff If the voltage exceeds a predetermined threshold, it is detected as a "trigger" event, and the pixel circuit outputs an event signal for post-processing by the peripheral circuit.

[0049] Specifically, as an external circuit, a two-dimensional encoder, also known as an arbitrator circuit, is connected. The initial program circuit 25 of the triggered pixel circuit sends a REQ_R signal to the Y-axis address encoder and receives an ACK_R signal in response. Furthermore, the triggered initial program circuit 25 sends a REQ_C signal to the X-axis address encoder and receives an ACK_C signal in response. Once the initial program circuit 25 receives the ACK_C signal from the arbitrator circuit, it sends an event transmission signal (Evt.Trans.) to indicate that a series of event signal exchanges with the external circuit has been completed.

[0050] In addition, the initial program circuit 25 sends an event transmission signal (Evt.Trans.) and simultaneously sends a reset signal to the sample-and-hold circuit, and turns on the switch SW. Therefore, the charge held in capacitor C1 is discharged, the reference level of the inverting amplifier's input is updated, and the next event detection cycle begins. That is, the hold value of the sample-and-hold circuit is reset, and the next sampling cycle begins. However, a large backlash voltage during reset could be a factor contributing to sampling errors in the input reference and leading to incorrect detection by the detector.

[0051] Figure 3B The operation sequence of the pixel circuit in the first embodiment is shown. In the pixel circuit of this embodiment, as... Figure 2 As shown, capacitor C F The two cascaded amplifiers 21 and 22, configured as NCG, are inserted between their input and output terminals. Furthermore, in the pixel circuit of this embodiment, when the output terminal voltage (V) of the inverting amplifier... diff When the voltage exceeds a predetermined threshold and is detected as a trigger event, the initial program circuit 25 sends a reset signal to the sample-and-hold circuit to reset the reference value used to detect brightness changes, without waiting for the completion of a series of event signal exchanges. Therefore, the recoil voltage during reset is small and does not affect the photocurrent input. Furthermore, since the recoil voltage is reduced within the settling time described below, the detection accuracy of the detector can be improved.

[0052] When the output terminal voltage (V) is detected diff Upon triggering, a reset signal is sent, a series of event signal exchanges with the peripheral circuit are completed, and the reset signal is released until the next event detection cycle (called the setup time) begins. In this embodiment, compared with the prior art, the setup time can be used as a preparation cycle for the next event detection, thereby improving the detection accuracy of the detector.

[0053] Second Embodiment

[0054] Figure 4A pixel circuit according to a second embodiment of the present invention is shown. The difference from the first embodiment lies in the capacitor C used for feedback NCG. F The arrangement is as follows. The source terminal of the MOS transistor Tr is connected to the cathode terminal of the photodiode (PD), which is a light-receiving element. The amplifier 31, with the connection point as its input terminal, outputs a voltage (V). log The voltage depends on the logarithm of the photocurrent, which varies based on the intensity of the incident light incident on the photodiode (PD). An inverting amplifier, including capacitors C1 and C2 and amplifier 32, is connected to the output of the sensor circuit. The output of amplifier 32 is connected to detectors 33 and 34, which can detect positive and negative brightness changes, respectively. The initial program circuit 25 controls the on / off switch SW and outputs an event signal for post-processing by the peripheral circuitry. In the second embodiment, an inverting amplifier 36 is connected to the output of amplifier 31, and the output is connected to capacitor C... F Connect to the logarithmic transformation output LOG-OUT.

[0055] [Equation 3]

[0056] C NEG =C F (1-A1A3)(4)

[0057] According to the second embodiment, by using a conventional inverting amplifier, a negative capacitance can be formed while suppressing circuit size expansion. Therefore, the parasitic capacitance (C) of the gate terminal of the MOS transistor Tr can be further reduced. g The effective load capacitance in a photodiode (PD).

[0058] Figure 5A modification of the pixel circuit provided in the second embodiment is shown. The amplifier 31 and inverting amplifier 36 in the second embodiment described above are configured to be implemented by a differential amplifier. The source terminal of the MOS transistor Tr is connected to the cathode terminal of the photodiode (PD). The logarithmic conversion output LOG-OUT, serving as a connection point, is connected to the inverting input terminal of the differential amplifier 41, and the non-inverting output terminal is connected to the gate terminal of the MOS transistor Tr and capacitor C1. A reference potential is applied to the non-inverting input terminal of the differential amplifier 41, which functions as an inverting amplifier for feedback control. The non-inverting output terminal of the differential amplifier 41 is connected to a sample-and-hold circuit, which includes an inverting amplifier and amplifier 42 configured as capacitors C1 and C2. The output of amplifier 42 is connected to detectors 43 and 44 that output event signals, and an initial program circuit 45 outputs event signals from the event signals for post-processing by peripheral circuitry.

[0059] In the modification, the inverting output terminal of the differential amplifier 41 is connected to capacitor C. F Connect to the logarithmic conversion output LOG-OUT. Since differential amplifier 41 is used as an inverting amplifier with gain –A1, no additional inverting amplifier is needed in the modification.

[0060] Figure 6A A circuit diagram of the inverting amplifier 36 of the pixel circuit provided in the second embodiment is shown. Furthermore, Figure 6B A circuit diagram of the differential amplifier 41 of the pixel circuit provided in the second embodiment is shown. The differential amplifier is shown in parallel with an inverting amplifier, which is typically used in pixel circuits.

[0061] Third Embodiment

[0062] Figure 7 A pixel circuit according to a third embodiment of the present invention is shown. Unlike the first embodiment, a buffer amplifier 56 is inserted between the output of amplifier 51 and capacitor C1. The buffer amplifier 56 can, for example, adjust the signal bandwidth and operating point.

[0063] Fourth embodiment

[0064] In the fourth embodiment, for example, the feedback capacitor C of the negative capacitance generation (NCG) circuit used in the pixel circuit is described in detail. F .

[0065] Figure 8A The capacitor C of the NCG provided in the fourth embodiment of the present invention is shown. F The structure is as follows. Interlayer capacitors are disposed in four metal wiring layers 61 to 64 of the substrate configured as pixel circuits. Capacitor CF Electrodes 65a and 65b are disposed in layers 62 and 63, and metal films 66a to 66f for shielding are disposed around them. According to this configuration, the capacitance C of the NGC... F It can be set in a substrate configured as a pixel circuit.

[0066] Figure 8B Another structure of the capacitor for the NCG in the fourth embodiment is shown. The in-layer capacitor is disposed in three metal wiring layers 71 to 73 of the substrate configured as pixel circuitry. Capacitor C F Electrodes 74a and 74b are disposed in layer 72, and metal films 75a to 75d for shielding are disposed around them. Also according to this configuration, the NCG capacitor C... F It can also be set in a substrate configured as a pixel circuit.

[0067] Figure 9 The structure of the variable capacitor in the NCG of the fourth embodiment is shown. In the variable capacitor circuit, multiple capacitor taps 810 to 81... n In the capacitor taps, capacitor elements CAP_0 to CAP_N, fuses FUSE_0 to FUSE_n, and test switches TEST_0 to TEST_n are connected in parallel in series. Correspondingly, capacitor tap 810 is connected to the power supply and ground via surge switch ROW_SEL. n Connect the surge switch COL_SEL to the power supply and ground.

[0068] Once the feedback capacitor C of the pixel circuit is determined... F To determine the required capacitance value, select the capacitor tap so that the total capacitance of the selected capacitor components meets the required value. The test switch for the selected capacitor tap is opened, and the test switches for the non-selected capacitor taps are short-circuited. Next, the surge switches ROW_SEL and COL_SEL are short-circuited, and the fuse for the selected capacitor tap is disconnected. Once all test switches and surge switches are open, the capacitor C... F The capacitors with the required capacitance value are connected in series between terminals 82 and 83.

[0069] According to this embodiment, a feedback capacitor C is arranged in the metal wiring layer. F NCG can be configured so that the capacitor elements do not need to be externally connected to the traditional pixel circuitry.

Claims

1. A sensor circuit, characterized in that, A connection point is provided between the source terminal of a MOS transistor and a photoreceiving element, and an amplifier is provided. The amplifier has an input terminal connected to the connection point, which is used to output a voltage dependent on the logarithm of the photocurrent of the photoreceiving element. The output terminal of the amplifier is connected to the gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage dependent on the logarithm of the photocurrent. The amplifier is a differential amplifier, having an inverting input terminal connected to the connection point, a non-inverting output terminal connected to the gate terminal, and an inverting output terminal connected to the connection point via a capacitor.

2. The sensor circuit according to claim 1, characterized in that, The capacitor is formed in a metal wiring layer.

3. A pixel circuit, characterized in that, include: The sensor circuit according to claim 1; A sample-and-hold circuit is connected to the output of the sensor circuit. A reset circuit is provided for resetting the held value of the sample-and-hold circuit if the difference between the output of the sensor circuit and the held value of the sample-and-hold circuit exceeds a given threshold voltage.

4. The pixel circuit according to claim 3, characterized in that, The capacitor is formed in the metal wiring layer.

5. A pixel circuit, characterized in that, include: A sensor circuit has a connection point between the source terminal of a MOS transistor and a photoreceiving element, and an amplifier having an input terminal connected to the connection point for outputting a voltage dependent on the logarithm of the photocurrent of the photoreceiving element. The amplifier's output terminal is connected to the gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage dependent on the logarithm of the photocurrent. The amplifier is a differential amplifier, having an inverting input terminal connected to the connection point, a non-inverting output terminal connected to the gate terminal, and an inverting output terminal connected to the connection point via a capacitor. It also has a sample-and-hold circuit connected to the output of the sensor circuit to hold the input voltage and amplify the change in the output of the sensor circuit. The pixel circuit includes: A capacitor inserted between the inverting output terminal and the connection point.

6. The pixel circuit according to claim 5, characterized in that, Also includes: A reset circuit is provided for resetting the held value of the sample-and-hold circuit if the difference between the output of the sensor circuit and the held value of the sample-and-hold circuit exceeds a given threshold voltage.

7. The pixel circuit according to claim 5 or 6, characterized in that, The capacitor is formed in the metal wiring layer.

8. A method for controlling a pixel circuit, characterized in that, include: A sensor circuit has a connection point between the source terminal of a MOS transistor and a photoreceiving element, and an amplifier having an input terminal connected to the connection point for outputting a voltage dependent on the logarithm of the photocurrent of the photoreceiving element. The amplifier's output terminal is connected to the gate terminal of the MOS transistor, and the gate terminal is regulated to a voltage dependent on the logarithm of the photocurrent. The amplifier is a differential amplifier with an inverting input terminal connected to the connection point, a non-inverting output terminal connected to the gate terminal, and an inverting output terminal connected to the connection point via a capacitor. A sample-and-hold circuit is also included, connected to the sensor circuit's output terminal, to hold the input voltage and amplify the change in the sensor circuit's output. This method is executed by an initial program circuit of the pixel circuit and includes the following steps: If the difference between the output of the sensor circuit and the held value of the sample-and-hold circuit exceeds a given threshold voltage, a reset signal for resetting the held value of the sample-and-hold circuit is sensed, and an event signal is sent to the arbitrator circuit. Once communication with the arbitrator circuit is complete, the reset signal is released.

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